Only if you presuppose that the "poo-pooing" of human social interaction has no value, or perhaps misunderstand the value of social conventions.

Even if you're brilliant and correct, a tactful approach to persuasion/discussion is virtually guaranteed to yield better results than verbal blunt-trauma. Unless the goal of life is simply "To be correct", which honestly strikes me as a fairly depressing end game compared to the other options.

No one's time is worth so much that they can't take an extra five seconds and think about how to say something to avoid looking like a jackass.

There's a difference between people who simply have poor social skills, where they'll say things like "You're obviously an idiot because that's the stupidest thing I've ever heard" and those who are assholes who say things like "All <people of race X> are stupid, just like you".

It's all degrees of asshole-ism, perhaps.

Calling someone stupid is another form of social poo-poo. There's no utility to it. Calling someone's action or behavior stupid, on the other hand, is direct and constructive. You are demanding that someone do something specifically different in order to improve. Calling the person an idiot is not constructive - it is only an insult. On the other hand, if the person said, "You're obviously an idiot because you consistently say stupid things, and you're dragging this project down, therefore I want you off the team," that may be hurtful, but it is constructive. It's a demand for change for the better.