I didn't know there where people calling Kojima sexist. But then, given how some people are, I'm not surprised.
I will admit that I am both a huge MGS fan AND I haven't played MGS5, but I don't think making a sexually idealized character necessarily speaks to one's personal politics. Could he be unintentionally sexist? Meh, maybe, but...who cares? Unless the man is walking around slapping women on the ass or saying they are inferior developers or something, I don't see an issue. And while MGS hasn't exactly been the most progressive series, let us not forget Meryl (in MGS4 anyway), Otocan's sister, and ESPECIALLY the Boss, all of whom were pretty good characters in their own right and weren't exactly sexually idealized (at least no more so than the reasonably good looking male characters). And while we're on the subject of revealing outfits, let's not forget that MGS2 had a whole segment of Raiden just running around naked. XD
I'm honestly not sure how Rose proves much of anything, though. I don't recall her being much more than a damsel in distress/really annoying love interest in MGS2.
I support feminist discussion in games (given that games are an art form and ought be critiqued as such), but anyone calling Kojima an outright sexist is a bit of a stretch. At worse he just doesn't care. XD