Seriously. It all depends on the context of the genre. When I sit down to watch a Pixar film, I don't expect the characters to act or talk like adults. When I watch a cop show, a drama, something adult that is going for realism, I do.
Like you said, is there anything more ridiculous than watching some foul mouthed NYPD detective tell someone to 'buzz off'. Basically, if you can watch that kind of totally unreal without being bothered or finding it utterly unrealistic, you must be an idiot or a laughably complacent media consumer.