Well, that is also a good point. He was scrounging, and suddenly he is handed powers and lots of minions. He then finds out a war is going on, and there are teams. Honestly, even knowing what he did to Yui, I felt bad for him when Shinji punched him, and then he was given a grief (and later stolen from) by Kitoka. Kitoka almost handed him a death sentence in his dealings with Asakura. I felt a bit bad for him there as well.
Basically, he just had my pity.. and as Takenoko said, he was given powers and did with them what seemed natural to him in the world he lives in. Either you are at the bottom, or you are at the top.. and if you are at the top you fight your way there and suddenly you are elite. He had no Uncle Ben to give him "the talk." ^_^ Though, if I had special powers, I would probably be a villian. I always liked Magneto.