I'm not really sure where you are getting this ivory tower view from. Pornography is not protected speech in the united states. The actual legal test as applied by our justice system for this "I know it when I see it" as applied under the Roth test. The practical effect of this is that our legal system is free to censor whatever it wants when it deems it necessary to. You seem deeply disappointed that our society as a result, chose obscenity quite often rather than censorship.

My general position has been that the durability of the Bill of Rights is directly attributed to what you call "relativism". When the government finds the Bill of Rights to be unpleasant, they simply decide it never applied in the first place.