The way I saw it was that Yaiba seemed like a parody of the way a lot of moronic gamers talk/act on the internet and in games. Not sure if that was intentional though. Even if that wasn't the case, it definitely seems like Yaiba is supposed to be seen as a bad guy, with Ryu being the honorable one.It's a combination of juvenile and cheeky to me, it seems.
It's definitely intentional because look at some of the other humor like the semi ramming in between the giant spread legs.
I'm pretty sure while Ryu is supposed to be some sort of "hero" ninja fighting for the greater good, Yaiba is just supposed to be an asshole. Maybe he's a sexist asshole... but nonetheless, I think he's supposed to have a very strong and potentially dislikeable personality.
There are sexist assholes in life. And it just so happens the main character of Yaiba might be one.
If the game itself promotes sexist messages (as opposed to being a parody, and/or having a sexist main character that you are supposed to dislike), then I don't see the problem with calling it out in reviews.