Yes, he is a true muslim. As long as he believes in one god and all of the prophets that muslims believe in, then he is a muslim. Swearing is not really haram, but it is ill-mannered and not the way a muslim should behave. As for fights, he is a boy, after all. Maybe he is just showing off? Meanwhile, if he takes drugs, etc. and acts like a PROPER gangster, then that is a major sin. Drugs are like smoking and alchohol I would say, since anything that harms you is prohibited. Try to help him become a better muslim in a way a boy may be interested in?
:salam2:
Sister Starz