Forum:Sandor, Why did he rob the farmer

Ok, I'm new to this, never read the books, got sucked in when they offered free HBO S04 premier marathon weekend. Binge watched all 3 seasons to catch up. Decided not going to read the books until series is farther along.

One thing that has been bothering me a lot is Sandor Clegane. When Arya asks him why he didn't leave Kings landing with loot he says to her "I'm not a thief," then he goes and robs a poor farmer and justifies it by saying the man is weak and doomed to die at the hands of someone else. Well, either you are a thief or you're not. And on top of it all it wasn't a crime of opportunity, it was a betrayal of trust. Here is a man who is able to take all kinds of abuse from Joffrey and serve loyally turning into a lowlife thug. Its not sitting real well in my head, any thoughts?