A movie that reflects real life is an opportunity to talk about the attitudes and issues you find distasteful in it (the movie, and real life).
It is a chance to get perspective on what we're taught when we're young. On how many of us, or our friends, thought about things when we were young. Amazing how the young can reflect so clearly both the good and the bad of a society, eh?
Getting drunk as a prelude to having sex is unbelievably, incredibly, common. And for most people it has nothing to do with rape (thank gods). It has to do with over coming your inhibition/phobia (socially constructed, I might add) of initiating or engaging in sex and making you more comfortable with yourself as a sexual being (again, socially constructed blocks here, especially for girls). The back and forth the boys have about their goals in this regard is probably the most criticized element I've seen.
Seth's statements (he's invariably the openly entitled male opinion) comes out of a patriarchal socially conditioned expectation that girls will not admit that they want to have sex unless they are intoxicated. As well as the fact that he is not exactly a "catch" by the same standards, thus his chances are slim to pull a girl like Becca unless she is "wearing beer goggles." As a result he figures his only chance to get sexual experience is through this method. Additionally, if it was only about getting the GIRL drunk (as I have seen suggested) neither Seth nor Evan would begin promptly drinking as well once they got to the party. Obviously alcohol was a part of the picture for them in their own minds as well. Most likely (this is my own extrapolating from how I thought as a teenager) to facilitate an "omg I was drunk" brush off should either party decide later that sexual activity was a mistake.
Engaging this movie (and really most Apatow) on surface value is missing the opportunity to talk about the problematic situations, and attitudes, that can arise out of situations like the ones in the movie. Presenting this out in the open, with what discussions even those two boys had about respecting women vs not, that is giving US the chance to take perspective from the film. While I didn't enjoy this film as much as Knocked Up, I did like it. I felt it (like Knocked Up) was excellent comedic satire.