Yes, I know how that feels, Duke. I was abused by students and teachers alike at my old Junior High - and nobody did anything but my father and Grandparents. I got robbed and those police did nothing because the thief was black, or whatever. I fought back on my own, and that earned me nothing but grief. I got in trouble, I got some people off my back, but others on it.
But, again - he'd be taking on a whole gang, a large group of thugs with knives and other weapons. Fighting back against one person might work well enough, but against a whole group like that? With such intent? He'd be going and getting himself killed/beaten again! That is not what would be advised, that would not help.
This is not a situation without victory. If he stays safe, if he lives happy enough, that is a win. And with this brought to attention, police will be more aware of the problem in his area. I'm sorry Duke, but what worked for you won't work for everyone. Especially not in this situation.