People are against it because several reasons.

First because it’s a very specific taste/opinion that they don’t share. You are saying that “all would be more appealing without softcore porn”, but it seems that you are the only one who thinks that here, most people don’t care or even like it. We could also put a filter to blurry dog pictures for people scare of dogs, where does it end? Until which point personal tastes should have their own explicit filters? It ends in a “word filter” which is already usable.

Also I would say that most people is against this because it reads as a first step towards a “porn ban”. We have no puritan advertisements or pay processor to please. People here like the freedom. And that would be a step in the opposite direction. It reads a little like so many discourses we are seeing in so many places to make them “family friendly” and to “protect the children”. I would suppose that due the nature of the fediverse (which is a push back against those people controlling our internet) is against anything that looks like that.