The difference is down to the power imbalance. It's the difference between those who are invited to laugh along as equals, and those who have to shut up and put up with being everyone else's buttmonkey. You can't laugh together over the absurdity of violence with the guy who's being kicked repeatedly in the guts. You can't wink and giggle over fat jokes with the chick who's constantly hearing the message that being overweight makes her less valuable as a person.
I get the same thing, though. I'm well away from being physically perfect yet I'm bombarded with the same messages and downright insults in the media, and if it's not that then it's because I'm dumb, incompetent, worthless, lazy, I overreact to minor illnesses or any of the other million things that the media uses to belittle men. I just don't see what makes women and overweight people so special that they can't be criticised.
On the other hand, I think it's worth looking at where these criticisms are being posted. They're on feminist and body-positive blogs. These spaces are set aside for discussing the particular issues that Fat Princess pings. A lack of criticism of violence in computer games doesn't mean that any given blogger doesn't consider it an issue. Rather, that the site where they're publishing has a mission statement which privileges particular kinds of posts.
And so it should have stayed there instead of becoming news on Yahoo. If they don't want their opinions to be circulated, discussed and made subject to criticism then they shouldn't post them on a publicly visible site.
Well, when you say mass slaughter of men, the reality is that those games are contextualized within a war.
Assuming that the people you are fighting aren't drafted, then they are there voluntarily and know the risks. It's not like you're killing innocent civilians in these games... unless you're playing GTA4.
How many World War II games, for instance, allow you to take prisoners instead of killing the enemy combatants ? It's entirely ridiculous, of course. Nobody wants to play Geneva Convention Simulator but that's the sort of game people who refuse to accept that they have no right not to be offended want.