Let's qualify that a minute. Jaime is usually polite, until such time that you push him too far, and then he's really blunt. I mean, there's the time he blows up his computer when talking to Oracle, just about every interaction with the Posse, his interaction with the Phantom Stranger (I ...think it was him anyway), the entire issue with him and Luis and the endgame arc where he blows up at those scientists who he is rescuing for stresses he's under because of the Reach.
I could probably come up with more when I fish my books out of storage.
Jaime is polite to his elders, definitely, but he is very much Beware The Nice Ones, to use a trope.