He got drunk and fucked a random girl he doesn't even remember. Please tell me that you don't think that this is somehow an "average guy" reaction to meeting one's ex, because if so, then you have a much lower opinion of "average guys" than I do (and it's moot anyway, since Peter is NOT an "average guy," and never has been).
Bottom line? Peter Parker's behavior should not remind me of a Seth Rogen character. This is the sort of emotionally stunted bullshit that I'd expect from Flash Thompson, except that even he has more maturity and decency than Peter now.