Wikipedia says that porn creep is about sexually explicit content entering American pop culture. It was outrageous forty years ago, but we must not complain about it now, because we might sound prudish.
It reminds me of the common arguments for why society should allow anything that was banned until now, such as homosexuals or women in combat. The common argument is not that our society would be better and happier if we didn’t ban it. The common argument is that it’s been going on for a long time. For example, historians will tell you that some women and some homosexuals have served in early American battles. Pornography has been around for thousands of years, holding an important place in many dead civilizations.
By that reasoning, everything will creep. Everything will become acceptable, given enough time.
I don’t accept that reasoning. Time can’t turn wrong into right.