I quite like this meditation by Noah Berlatsky on cheesecake and precisely why drawing superheroines as pinups as offensive, and just plain incompetent:
If you make it simply about visual stimulation, it’s simply about visual stimulation, and doesn’t have to have anything to do (or at least, not much to do) with real women. Once you start pretending that you’re talking about a smart, motivated, principled adventurer, on the other hand, you end up implying that said smart, motivated, principled, adventurer has an uncontrollable compulsion to dress like a space-tart on crack. Which is, it seems to me, insulting.
The second thing is that, if you must make your adventurer into a fetish object, it seems like the least you could do is make her tough…if you’re going to do action-hero cheesecake, then bring on the masochism: get off both on how hot the action hero is, and on how thoroughly she can beat you black and blue. It’s feministsploitation; not feminism exactly, but a fetishization of feminism, and it makes some sense at least to the degree that the fetish clothing and the putative power of the character are coherently working together, both in that the power makes the character more sexy and in that that the clothing adds (not necessarily logically, but still) to the sense of the character’s potency.
I basically agree with Noah: there’s nothing essentially wrong with producing sexy depictions of everyone. The problem comes when you mash up two projects in a way that undermines both: so-called sexy superheroines are drawn in a way that undermines our sense of their competence and power, and the things illustrators do that are meant to make them sexy often show more ignorance of the female form than appreciation for it. Sexist justifications for the depictions of female superheroines often get more contortionist than the heroines’ poses, and there’s something oddly refreshing about Noah pointing out that the guys who want hot depictions of powerful women are undermining even their own interests.