Philosophy professor and prolific author Dr. Ed Feser has a lenghthy post on the Prop 8 overturn. I’m just picking out some highlights. I suggest you read the whole thing. The dialogue in the comments is worth looking at also.
1. Judge Walker’s decision, he tells us, is based on the principle that the state ought not to “enforce ‘profound and deep convictions accepted as ethical and moral principles’” or to “mandate [its] own moral code.” But that is, of course, precisely what Walker himself has done. …What we’re seeing here is just one more application of the fraudulent principle of “liberal neutrality,” by which the conceit that liberal policy is neutral between the moral and metaphysical views competing within a pluralistic society provides a smokescreen for the imposition of a substantive liberal moral worldview, on all citizens, by force….
2. As with other issues, what will decide the “same-sex marriage” controversy in the long run are the attitudes that prevail in society at large, not this or that judicial decision, ballot measure, or piece of legislation. If a solid majority of citizens continue to oppose “same-sex marriage,” then it can be stopped and liberal advances can be turned back. …The advocates of “same-sex marriage” are motivated by a moralistic fervor, and their position rests (whether all of them realize this or not) on controversial metaphysical assumptions about human nature and the nature of value. If they are effectively to be rebutted, they must be met with equal and opposite moral and metaphysical force.
Unfortunately, too few conservatives are very effective in this regard….
There may be limits in practice, but there are no limits in principle, to what liberals might come to endorse, and be willing to impose on all by judicial fiat, in the name of “justice.” No doubt most liberals do not at present advocate infanticide, mandatory euthanasia, “group marriage,” incest, bestiality, mandatory vegetarianism, mandatory organ harvesting, and the like, but there is nothing whatsoever in the “logic” of liberal arguments for abortion, “same-sex marriage,” euthanasia, “animal rights” etc. to rule such things out. Indeed, there is nothing to rule out even more bizarre and as yet unimagined practices than these. …
This is not a slippery slope argument. The point is not that liberalism will lead someday to something truly nasty. It has already done so; indeed, it is itself truly nasty. As Alasdair MacIntyre put it in After Virtue, our choice is between Aristotle and Nietzsche, between submitting ourselves to the natural order or instead to the will to power of self-appointed “revaluators of all values.” In the person of Judge Walker, Nietzsche has spoken.