Anybody notice a key difference there?
If you said, "Hey—those dudez aren't naked! They're just in white-person flesh-colored body stockings!" give yourself 1,000 points.
Now, there are a couple of issues at work here. One: The obvious double-standard regarding male and female nudity.
Two: The issue that even when women do what they're meant to do by the fucked-up standards of The Patriarchy—get naked and submit themselves for public objectification—they're going to get mocked for doing it. Because, even though we're ostensibly laughing at the Judd Apatow Boyz for their uproarious send-up of a sexy female-oriented VF cover, implicit in that laughter is a condemnation and marginalization of the female-oriented cover: See how silly it is when a man does it?! Ho ho ho.
Three: Fat-hating. Obviously, Jonah Hill's and Seth Rogan's fat rolls must be hidden safely away behind unitards, lest anyone who views their bodies come away with the mistaken impression that not having a perfectly sculpted body is okay. (ZOMG THINK OF TEH CHILDRENZ!)
Four: While Paul Rudd sniffs Seth Rogan's ear dreamily, I catch a whiff of playing gay for laughs. Mind you, I suspect Rudd and Rogan regard their pose as deeply ironic, intended to fuck with the conventions of homophobic dudez—but there's the usual inherent problem to privileged ironic humor on marginalized classes of there being no distinguishing commentary. A genuinely homophobic dude could look at that picture and laugh at it ("Fags are funny!") instead of laughing at his own terribly misguided homophobia.
That's off the top of my head. I'm sure you'll tell me what else is wrong with this fuckery in comments.