Yeah, if this wasn’t an abuse of power, or otherwise using his position, it’s just sex.

Yeah, fucking in the office is pretty stupid, but I don’t think anyone should be fired just for that. Demoted, maybe. Given a stern warning, absolutely (and eventually shit canned for repeats, but only because sex is messy and that’s shared space). But being punished for having sex? Fuck that, it’s stupid, and the idea can fuck right off