Unless you're talking about literal rape I don't know what their weight has to do with it, but it should be more about keeping pedos, hebes, furries, trannies, groomers, and other sickos out of the classroom than considering how the victim "feels" about it or whether or not they are really a victim. Obviously it depends on the age-gap but there's something wrong in the head about a woman who has sex with her underage student - even if it's intuitively different to you or anyone.

So I agree with you that's one reason for different treatment, but don't agree that disagreeing is misguided or pointless.