So, a while back I re-read Dragons of Autumn Twilight, just to see how it held up. And it came across to me that while they are not nice to him, that's because he has been walking around haughty, disdainful, and rejecting their overtures of connection for years before the actions in the novels begin. Raistlin is filled with self-loathing, and he projects that outwards, to predictable results.
Raistlin is, in the end, a sullen teenager turned up to 11. Teens will identify with Raistlin's stance. However, in an adult, this is toxic behavior. Raistlin's treatment of Caramon is outright emotional abuse. We cannot excuse that by, "Sturm's kind of a dick to me." If you are a passive-aggressive, self-centered abuser, other adults will, and should, treat you badly.