I see your point, but the sexism you speak of comes from our assumption that the poster is male because he likes boobs (not necessarily true), and our consequen

I see your point, but the sexism you speak of comes from our assumption that the poster is male because he likes boobs (not necessarily true), and our consequent conclusion that "he" is implying the readership here is male. As you say, the mere expression of a personal sexual preference is not sexist in any way. People use Tinder to find a sexual partner for themselves, so any criteria is fair game (even if it may cause eye-rolling). Now if it was being used to select Nobel Prize-winners, saying "what about boobs?" would indeed be intrinsically sexist.