Fair enough, Neko_Ali, I didn't realize that both parts of Thrillho's comment were referring to the realism of the situation, and I thank you for helpfully explaining that.
However, the jokes I like are the ones where the thing that is dull and realistic is the person being an ass, and the enjoyable thing is, for example, that the transphobe is shoved out the door by Emily mid-rant, or that the sexist store clerk is reprimanded by Sam, and that is indeed a uncommon and unlikely thing to have happen, so that makes it work as a joke.
If the joke is instead that someone is an ass, and then gets away with it, there are two problems with that. One, the unrealistic thing cannot be that they are more rude than people in reality are, because the ceiling for absurd rudeness in Questionable Content is significantly lower than in reality*, and any rudeness in the comic is therefore dull and realistic. Second, the unrealistic thing cannot be that they get away with being an ass, because that is often the default in real life, and is therefore dull and unrealistic.
Mind you, the above is not true for everyone. It is entirely possible that there are people for whom the default is that people are not very rude at all, and that any rudeness that does happen is swiftly discouraged. If that is so, I am very happy for them. I mean, I would love for rude people to be so absurd an idea that someone being rude and getting away with it was something unrealistic and absurd. That sounds lovely. I just mean that that kind of joke cannot work for me.
*For example, the real life version of the university Marten works at has not been so accepting of trans students as the Questionable Content version.