I think for a lot of people it probably stems from a desire to have a way to identify all rapists and pedophiles, so I think the idea is to have these broad categories and easily identifiable markers of what indicates that. Unfortunately, not only does that fall far short of the goal of identifying all perpetrators, some of whom are exceptionally good at cultivating a 'wholesome' personality for whatever space they're in, but it categorizes a lot of perfectly innocent people, some who may even be victims of sexual abuse, as offenders. Which is the same issue that sex workers suffer from, with innocent people and victims of sex trafficking being criminalized along with the offenders, and with offenders, who are more unscrupulous and often have more resources than victims, having a much easier time evading the law. Maybe that parallel needs to be drawn more, for people on the left who already see that treating sex workers that way is not a viable solution to sex trafficking and exploitation, but who maybe don't see the problem with applying that sort of reasoning to everyone else.