I believe my uncle has been discriminated against at work

My is a mechanic and was let go from work yesterday. His supervisor said that he had to let him go because he was not "steping it up" at work. When my uncle asked for and explaination and permission to record the converstion his supervisor said that since he wanted to record their conversation that my uncle would need to wait until the big boss got there he told my uncle he would call him when the big boss arrived so my uncle left. My uncle went back to this employer today and he had the opportunity to speak to a co-worker and the coworker told my uncle that their boss had approched him and told him that "the mexicans were dropping like flies" and that he only had a few more to go before they were all the mexicans were out of there. My uncle did record this conversation with his co-worker and left. Would he have a case? He has yet to receive a response as to why he was "let go" as his supervisor put it. He has not had poor performance reviews. My uncle feels he is being singled out by this supervisor. My uncle has a family of 3 to support and he is the main bread winner in the home please help me help him.