I've had personal friends that I have defended when they did something wrong. Always because there was no ill intent and it was a mistake.
Stealing? That's different. There is never an excuse. It always carries ill intent. Stop trying to defend someone who has taken someone else's things as their own. He's an adult, he made his own choices. Who cares if he's an addict? Seriously? Been there - done that, never stolen anything. Ever. The guy is selfish and does not care about others other than himself.