He's Just Not That Into You has the structure of an dialectic between passionate, but very drunk, people: the Realist and the Cynic.
The Realist starts out with a heartfelt tirade about how women are so willing to make excuses for men when they act like assholes, when in fact men are dogs who all just want to sleep with Scarlett Johannsen. The movie demonstrates this point by having its main female characters make cringe-inducing excuses for the assholes in their lives. The adorable GiGi (Ginnifer Goodwin) becomes an adorable quasi-stalker after going out on a single date with a blah real estate agent named Colin (Matt Dillon's brother, I think) who actually likes Scarlett Johannsen, while Beth (Jennifer Anniston), who wants to get married, stays with her boyfriend Neil (Ben Affleck) even though he's made totally clear that he's going to marry her, and Janine (Jennifer Connolly) obsesses over her home renovations while the college boyfriend she forced into marrying her, Ben (Bradley Cooper) lusts after, of course, Scarlett Johnansen. The Realist belches loudly and rests her case.
The Romantic cannot bear this, however; she feels that the Realist is being not only one-sided, but fairly sexist. Swaying slightly, she stands up, forgets to mention the sexism issue, and gives a rousing, if incoherent, speech about how if women are fooling themselves into thinking there's a chance with some asshole, at least they're maintaining hope rather than being cynical and treating the opposite sex like objects, man. On the movie plane, Gigi delivers this speech to Alex (not sure who this actor is), the bartender who had been channeling the Realist by explaining how if a man wants to see a woman he'll make it happen and is thus rejecting Gigi.
The Realist cracks another beer and counters that, yeah, but still men are definitely dogs because they definitely all want to sleep with Scarlett Johannsen, because she has boobs the size of planets and acts so vapid she seems to be sedated. Whaddaya say to that, huh, Romantic? Ben sleeps with Scarlett. Then, in order to really make the Realist's point, he tells his wife that he slept with someone but that he doesn't want to get a divorce, but then he starts to get it on with Scarlett again, in his office, then sticks her in the closet when his wife arrives to try to save their marriage, and then gets it on with his wife instead while Scarlett hides. Scarlett wears Little Bo Peep-type dresses and undergarmets in order to emphasize her planet-boobs, and acts vapid to the point of being sexily comatose.
The Romantic makes huge dismissive gestures with her arms and raises her voice to make her point: Yeah, planet-boobs, etc., OK but Scarlett is hurt in this scenario too, what with the hiding in the closet! And, it's just not realistic to think that women will stand for this kind of crap forever! Whereupon Scarlett huffs out of the closet, Beth breaks up with Neil because he won't marry her, Janine throws out Ben for being a lying sack of shit, and Gigi moves on from Alex.
The Romantic isn't done yet, though. Pounding her fist on the table and knocking her drink over for emphasis, she says that true love really does exist! Sometimes men who have seemed like assholes really just needed that one special woman to unlock their inner teddy bear, just like in the movies! The Realist tries to interrupt--Scarlett Johannsen! Perpetuating unrealistic--but she is no match for the Romantic's sheer volume. In a whirlwind, Beth and Neil get back together and he reverses course on his heretofore consistently held no-marriage philosophy; Janine kicks Ben out but she still believes in love and is starting to date again; and Alex, the cool cynic, realizes that he's head-over-heels in lurve with Gigi. Swept up in it all, some peripheral characters--Connor the real-estate agent and Drew Barrymore, who has been hanging out around the edges of the movie, get together, and Scarlett Johnannsen goes to India on a yoga retreat (good riddance)!
The Realist gives up and goes to the bathroom, and the Romantic declares victory, ends the movie, and passes out on the couch.