when I was a kid, all of the cussing and violence I learned were either from friends or at school (or TV).
there's a chance he learned it from his parents or other family members, but there's also a good chance he didn't.
Its not just violence and vulgarity, but it also takes a certain mindset and a degree of confidence to do that to an authority figure given school is designed to condition you to seek their approval.
"How is that a religious topic? That's just me talking about GOD." -Frostmourne