Disclosure: I have zero interest in the movie, since Watchmen never struck me as a particularly compelling story. So, I haven't seen it, and I'm probably not going to talk about anything plot related. You've been warned...
Something interesting that I recently stumbled across in one of John McWhorter's books is the idea that there are discrete "levels" of formality in relationships, and language-based awkwardness or offense tends to arise when one party "jumps" more than one level at a time. As a polite example, when one addresses their friends as "ladies and gentlemen," it's either taken as a joke or feels odd. I wonder if that's a big factor, here, where one's relationship with the story affects their reaction to key incidents.
I point this out, because often when I mention disliking Watchmen among other fans, I'm told that I didn't "get it," and that a lot of the story was meant to be ironic (and, thus...uhm...I wasn't supposed to enjoy it, I guess). In the context of irony, it seems like the objectionable scenes actually fit better with the story, especially when I (vaguely) recall Moore back then talking about how superheroes were all really fetishists repressing sexual and violent tendencies.
That's not to excuse it. Something I've recently been discussing with friends is the idea that a creator needs to somehow "earn" the right to be vulgar first by gaining the audience's trust and second by integrating it with the rest of the routine. I use George Carlin as an example of someone who went VERY far out of his way to earn the trust of his audience, and (with the exception of people who are genuinely offended by concepts themselves) could therefore get away with using whatever sort of language or metaphors he chose. Contrast with someone like Dane Cook, who randomly blurts out profanity and talks about sex.
Heh. For those who'll say that sex and violence is "real"? Well, first, I question what reality such people live in, because around here, both those things are frowned upon in polite company. And second, maybe creators need to earn the right to use reality in general...
Anyway, what goes for standup comedy, because of the different structure, goes double for drama, in my eyes. Since the goal is to keep the audience's attention inside the created world, elements that are too discordant at once (see my original McWhorter idea--you didn't think I'd forgotten, did you?) pull you out too quickly, because there's not enough trust built.
Am I closer to the target on the scenes in question? Because it sounds like the real complaint is that the narrative didn't support the scene and that the scene was too prominent, rather than itself offensive. In a different movie, everybody seems to agree, there wouldn't have been anything wrong. To me, that sounds like the movie fails as a work, not allowing you to suspend disbelief.
(Meanwhile, I'm still trying to wrap my head around the idea of Watchmen being supposedly "unfilmable." It seems straightforward to me, once you eliminate the supporting documentation that, in Moore's on words, was "filler." Because he sold the series as twelve issues, but could only come up with six issues' worth of script, in case anyone was curious.)