Rape jokes and the white guy using the 'n' word. WTF?

There were some really big laughs in this film, including the whole stuff with the airbags, when Rogen lamented that his baby daughter's first word would be 'cünt', and the part when Rose Byrne is screaming about her breasts, and shouts "You Jews and your mothers!" at Rogen (the fact that a large proportion of the people involved in this film are Jewish, mitigates any concerns about anti-Semitism), but there were also a lot of dodgy allusions to rape.

The frat boys brag about placing a penis in one of their pledge's mouth whilst he was asleep, Efron keeps trying to force a dildo in Rogen's mouth, and Efron scares his neighbours with a threat about all the horny frat-boys who will be living right next to their young daughter (I'm not necessarily suggesting that he was referring to some sort of paedophilia, but even if he was talking about Stella when she got older, it was still a pretty dodgy and presumably rapey allusion).

And then there was the moment when the couple and their best friend were imitating celebrities over the airways in order to get people to gatecrash the fraternity party. It starts off really funny, with some almost pitch-perfect imitations of Mark Wahlberg and Ray Romano, but what was with the final Obama impression and the 'my n*****s' signoff. Is it acceptable now to have a white guy do an impression of a black man whilst using the 'n' word, a word Obama would never use? I realise that's the entire joke, but it seems very dodgy and borderline racist to me, especially in a film made by, and predominantly featuring, white people.