I certainly can agree with a rating, category, flag or other notification similar to movie or game ratings. This is a restriction or advisory, not censorship.
I disagree with straight censorship, making something unavailable.
Most of us know someone who is religious (pick almost any religion) and intolerant of other religions. Those people are disgusted that we can buy books about other religions and/or offended by books that somehow denigrate their own religion or religious figures. Just be prepared to have your own religious (or atheist or agnostic) beliefs censored.
Perhaps more on-point, violence is a far greater (widespread, common, pervasive, equally damaging) threat to our society than deviant sexuality. Why are we not more disgusted with books that have extreme violence in them? I'm not suggesting we censor those either, quite the opposite.
I do not expect to change your mind. Those who throw stones rarely recognize how slippery the slope is they are standing on.