There are a truckload of people, particularly in academia, who believe that the notion of a slippery slope is bullshit and should not be a valid point of concern for conservatives. It's actually considered a fallacy, albeit a tricky one where the premises make all the difference. But liberals are the ones who deny they exist, because conservatives are the ones who invariably get screwed by slippery slopes when they happen.
Conservatives defend the status quo, pretty much by definition, in tangible structures or in values or whatever. When disagreements about change versus status quo come up, a compromise inherently supports change. You can see this easily if you imagine the disagreement as being between two points which meet in the middle; if you go away from the status quo - particularly in a direction opposed to the ideas that legitimize that status quo - then you've begun a process and undermined that status quo. If a new grievance comes up and compromise is reached again, then there will again be a move away from the first compromise point, further away from the old status quo. If you're a conservative and compromise becomes the norm, then you're moving in a direction you don't like and the only thing being controlled is the rate of change, like trying to paddle upstream and away from the drop-off of a waterfall.
This does happen. Constantly. Particularly for a historian, it's rather awe-inspiring that anyone could say that patterns of change moving in a certain bad direction are not a legitimate concern. Everything from the gear-up to war to the rise of the Jonas Brothers becomes disturbingly predictable when the trends start to make themselves known. Of course those patterns happen; the disagreement is really over the direction of the change, whether that direction is good or not.
So, too far or not far enough, that is the question for liberals. It doesn't matter that much, of course; eventually, they will get to where they want to go. If today's society isn't "ready" for the changes that they want, then they move incrementally, and eventually, the change becomes the new normal and they can move the rest of the way after people have adjusted to it. Adaptability is key; talking about gay marriage, Jonathan Haidt recently said gays getting married was like sushi, where earlier generations were repulsed as a matter of taste, but younger generations like it fine, having been more exposed to homosexuality. He's right, although there is the implied liberal notion behind this statement that all tastes are equal and unrelated to more fundamental issues. Haidt would never think most people will ever simply lose their taste for marriage altogether as its expansion and changing social expectations weaken the tie, because he thinks of marriage as being a natural human relationship needing no encouragement. I don't. He doesn't think of marriage as being a cultural institution that needs necessity or ideological legitimacy to survive. I do.
Slopes and Sex
The most radical example of the slope has been sexuality over the last 70 years, as we've spent this time creating a social environment where people can do whatever the hell they want. This little incident happened at a rap concert recently, and I got into a conversation about it on Facebook that led to many a facepalm.
So a rapper got a blowjob in front of his audience. What does this have to do with the slippery slope? A lot. Long ago, society had enough confidence in traditional notions of morality that a band of concerned fathers probably would have beaten the shit out of all involved with the encouragement of their wives, but a gradual wearing down of the infrastructure of Western ethics has destroyed that strength, and the standards of behavior that were enforced with it.
In raw liberal principle, there's not much wrong with public sex acts, if you're assuming that it's wrong to push your beliefs on others. Both classical and modern liberals promote maximizing individual autonomy. We have no grounding to complain when we see this, except in the sense that you just didn't feel like seeing it, in which case you shouldn't be going to a rap concert. It's not your business. The libertarian bunch I talked to made their arguments as if there was a question of male molestation or rape here, which is absurd when you notice the rapper tweeting about the experience with pride. The real reason people are disgusted is because the culture of rap is disgusting to them (and to me). It has been for decades. But libertarians pledge themselves to hands-off freedom, and can't really say anything. Liberals can't say much either, as they have been tied to sex-positive feminists and have been assaulting religious repression of sex for too long to turn back now. They find it disgusting, too, but like the libertarians, they have no grounds from which to complain. They are simply more likely to understand that it's their ingrained, subjective preferences at work, and they will tell themselves to be less judgmental.
It's tempting to go along with them and say it doesn't matter, but it does. Living in a society where skank behavior brings no consequence isn't just ugly; it's hell on commitment. We've been moving towards loosening the tight cultural grip on sexual behavior for three generations now, with the help of contraception and abortion. We are, by the old standards, a society of honorless whores. If you take sex, and the high valuing of the sex act, to be intrinsic to relationships and marriage, then you might see this whorishness as a major culprit in the decline of marriage. It's not enough to pay lip service to sex being about love. Sex is extremely difficult to control, always having required more than a simple programming job on the individual, but that control is necessary to creating a social environment conducive to maintaining a commitment. Relationships do not happen in a void. If you live in a culture of honorless whores, and your choices of mate and social environment are dictated by that culture, then your sex life will not be under your control because you do not live in a society that enables you to expect the monogamy that comes with a moral attachment to sex. And we don't. Most of us don't have the power in relationships to demand unusual terms when we get together with someone. Sex is more public than it was in every way, and society's expectations must become our expectations, since those are the requirements people will live up to. We aren't quite there yet, but we will either abandon monogamy as a condition of relationships or simply shorten the expected time that relationships will last in response to these changing tastes.
Similar slippery slope cases can be made about financial accountability, about the treatment of old people, about education, and about religion. Every person has a sense of justice and right action that has been instilled in them by their culture; when we emphasize individualism with law and rhetoric over conforming to the standards of the society, then we lose a fundamental method of control that allows ANY sense of justice to exist. Culture, with its authorities and norms, define justice by defining expectations. When we strip them of their power, we encourage the sense of anomie that Durkheim talked about, little by little, generation by generation, as the strictures fall apart. What for? For liberation. For power. For the sake of destroying an old hierarchy, one which the alienated view as unjust. They do not accept their standards. They do not accept the legitimacy of their values. And yet, they do not proscribe new values and form a new hierarchy, only the prerogative to follow whatever values work for you, refusing to take on the task of culture. That's their angle, their tactic, working in spite of their own binding ideology that they refuse to put real stock in. If you believe shared values are necessary for society to be a society, then this means trouble.
As a general rule, liberals seem to like change for the sake of change. Underdog lovers want change because it undermines the power structure. The worst possible scenario for them is for any group to end up with power long enough to institutionalize their values and undermine equality, so they are always throwing bombs at the status quo and talking up change as if it's good in its own right. Many people disagree with this intuitively, but the debates are never framed this way and the majority of Americans probably do see change as generally good.
It's important to remember that liberals validate themselves by supporting the underdogs and hounding the powerful ruthlessly; it creates a sense of righteousness to protect the weak against the strong, as most Westerners - not just liberals - understand. They have their reasons for believing themselves to be the heirs to the Western intellectual tradition. In fact, I'd say that they are, descending straight from Locke and company. The results of a liberal society show the weaknesses in that tradition.
For the conservative, it's different. The conservative is a firefighter. His perspective is one of trying to put out most of the blaze and preserve the structures which retain value, only allowing the worthless ones to burn. He understands that it's easy to pick nits with any given structure, hierarchy, or situation; it's harder, although more worthwhile, to understand why things are the way they are and to recognize the positives while realistically assessing the pitfalls of change. It's impossible to do this if there are severe points of values disagreement between the individual and the society, and making equality itself a goal kills the potential for legitimate hierarchy and legitimate action, creating a unique type of stagnation: internally roiling but, when viewed from the outside, in a type of stasis.
Both sides are fighting for their self interest, although they often accuse the other side of being oriented on materialistic, individual power, which is not necessarily accurate. Conservatives aren't all beholden to fundamentalist religion or the Koch brothers, any more than liberals are just trying to use the government to steal money from the rich. This goes to the core. If someone holds on to a set of ideals as their own, even if they aren't powerful within the hierarchy that emerges from those ideals, then trying to supplant those ideals with competing ones is an attack on their identity. This must be the case: men have willingly died for ideals before, which indicates an extreme lack of material or political self-interest to the point of self-destruction. Why? Because the ideals being upheld were integrated into the identity of that individual and defending the ideal becomes synonymous with defending the self. A victory for those ideals is empowering to the individual who has integrated them into their worldview, even if there is no more tangible benefit than the perception of being on the victorious side. What matters is the side you take. Call yourself a universalist and talk about unity all you want, you don't want it so badly that you will give up everything you believe in. Any given individual is more than just the shallow welfare of a couple hundred pounds of flesh. They radiate out, form bonds with others, and become part of something larger. If they don't, they deserve only pity.
It's very easy to look at the world and say that the conflicts are the problem, that people should be more peaceful. But as long as anything has value to anyone - including their own identity - conflict is at some point inevitable. And, for that matter, healthy. The conflicts are not inherently evil and the willingness to bow to others is not inherently good; that's a fiction created to create peace among those in the lower orders, for everyone's benefit, long ago. They need it, lest the higher order destroy them out of self-defense or simple irritation. They need it, because they do not have the ability to play the games at the top level. There IS a hierarchy for any given order. The choice is not simply one of ideas but one of what culture, hierarchy, and identity you become a part of. Whichever order you choose defines much of who you are, and it isn't a question of calculating costs and benefits. The decision supersedes costs and benefits, because the decision molds the values from which you make the calculation. For most people, it isn't a choice - you don't choose the values and ideas you are exposed to - so much as a realization of who you are. This is where a person, consciously or unconsciously, looks at their life, their culture, and their identity, and says "yes".