>>212916089Sam loves irony and shock value because they give him an advantage over whoever he's interacting with. He sees comedy as a power play, which is why so much of his comedy is about humiliating random Craigslist actors. It's sadism. Funny sadism, sometimes, but everything he does is about bolstering his own ego specifically at the expense of others and that's what "humor" is to him on a fundamental level.
When Harland said "You look like you've been raped before" Sam realized he was dealing with someone he absolutely could not intimidate, bully, rattle, or exert any power over using his usual methods. Since he sees comedy as an interaction of power, the fact that he wasn't "winning" meant in his mind that he was somehow "losing" and he absolutely had to correct that. He got physical out of paranoia and insecurity.