He likes to hurt people because he was hurt, it’s a process of healing for him. Feeding on the weak and insecure he feels powerful. There are better ways to cope with his pain though and he will find out eventually. I am sometimes rude to people too, often explain to myself that it is for their own benefit to toughen up, while in fact it is just a projection of my own insecurities. Naturally it doesn’t help but makes you even more insecure.