Former Jezebel editor Jessica Grose writes on Slate that after seeing the movie she found the date rape scene to be:
... just another stomach-turning plot point in a movie consisting of several similarly revolting scenes. If you are to take the film and its characters seriously, which perhaps is beside the point, Rogen's cop not only sexually assaults Faris but basically stalks her, and the movie ends with him publicly slut-shaming her.
As Jessica points out, in an interview with the Onion's A.V. Club director Jody Hill said he thinks the scene would have been even funnier if he left out the line some have construed to mean that Faris's Brandi consents to the sex (even though she's passed out):
JH: [Pause.] I dunno. I've always kind of liked scenes that you talk about how fucked-up they are. I would have been happy without any dialogue in that scene. I wanted to show them just having sex and her passed out, and I thought that would have been funnier. But I think I have a darker sense of humor than most people. So at the end, [Faris' character] is okay with it. [Laughs.] And that was like, "I'll shoot it both ways." So I actually shot it both ways. I just kept the camera rolling. There's like a line that's "We're okay laughing, and you're pushing the envelope." But you're not really pushing the envelope until you cross that line where a lot of people don't go along with you.
Hill goes on to praise Seth Rogen for standing up to the studio when they wanted to tone down the many disturbing scenes in the film, saying Rogen "really is a fighter for what he believes in." In a separate A.V. Club interview with Anna Faris, it seems that she wasn't as happy with the rape scene as Hill and Rogen, and actually assumed it wouldn't make it to theaters:
AVC: What did you think of the script for Observe And Report when you read it? Did you have a sense of how dark and tonally edgy it would end up being?
AF: Honestly, I didn't have a very good sense at all. [Laughs.] I mean, I read the script and I auditioned for it. I had to fight a little bit for the role, and I wanted to be a part of it so badly. I had seen Jody Hill's Foot Fist Way and loved it. Danny McBride, I loved. The unapologetic nature of Jody's comedy was so appealing to me, and I really wanted be part of it. I'm so grateful I was cast, but when I read the script, I thought, "Well, this is Warner Brothers. This is a studio movie, so this is all gonna be softened up. It's a comedy, right?" So when we were shooting it, even the date-rape scene-or as I refer to it, "The Tender Love-Making Scene"-I just thought, "We'll shoot it, but it's not gonna be in the movie. I don't have to worry about that one." And yet there it is.
Faris adds that she wanted to do the film because Brandi was so awful, since apparently she's having a hard time finding studio films featuring stupid, slutty female characters. She explains:
[Brandi's] really vain, she's really bitchy, and I always imagined she was incredibly stupid, too, but it was just a joy and delight to play her. It's not often you get to be that naughty. It was wonderfully shocking. I read a script where the lead female is so awful, and I was like, "This could not be a studio movie." So it was just a joy.
Blogger Majikthise explains that in the film Brandi's character, not just the one line she mumbles while drunk, are used to justify the rape. She writes:
[Hill] also makes Brandi's character so shallow, manipulative, drug addled, and "slutty" that the target demographic feels she deserves what she gets. Brandi's character is noteworthy because she [has] no redeeming characteristics whatsoever. Even Ronnie has his good points, like his tenderness towards his falling-down drunk mom, and his refusal to steal from his employer, and his heartfelt thirst for justice. I defy anyone who has seen O&R to cite an example of a good, or even neutral, characteristic of Brandi.
So it seems the early reviews were right: The rape isn't so bad when viewed in context, but only because Brandi is treated horribly throughout the film. Hill didn't intend for anyone to mull whether the sex was consensual or not, he just flippantly tossed the date rape in the film in an attempt to get some laughs.