It is true, nobody actually dislikes sex (or they wouldn’t exist). Possible exception: asexuals, who are in fact genophobes.
“Sex-positives” are odd ones, they come across as sluts trying to justify lack of impulse control. It’s like FEMEN protesting objectification by getting their tits out. It isn’t about sex per se, they misrepresent, it’s about casual sex, but most people approach the idea of sex with some respect, borne of the serious ramifications and consequences. They’re anti-monogamy because they can’t secure that level of investment.