Can my husband file a lawsuit?

Ok a few days ago, my husband was fired from his job of 3 years. His supervisor let him go because he said that he was just doing his job and going home and not thinking outside the box (my husband was the custodian of a gym.)

Ok this is what happened. The Gym is owned by guy A. His sister, who was the district manager hired my husband 3 years ago. The gym's manager is guy B. Now about a year ago, my husband had an issue with guy B regarding his annual raise.When guy B be threatened to fire him over questioning his authority, my husband called the district manager (the sister), who then resolved the issue by giving my husband what he wanted. A few months later, Guy B told another employee that he wanted to rid himself and the establishment of my husband, but he didn't have any dirt to pin on him and he didn't have the authority to do it, because the district manager wanted to keep my husband there.

Then a few months ago, the district manager (the sister) was moved to a different location, and Guy B was promoted to her position. Next thing you know, my husband has his hours cut, he's doing the work of 3 people, and Guy B says if he can't get all his old work, plus the new work done in the time he's given, he'll be let go. A couple of weeks go by, and my husband is fired.

Then we find out that Guy B has been advertising to replace my husband since he's been in his new position. We literally found advertisements that we never would have seen because my husband wasn't job hunting at the time, but once he started looking, he found ads that dated months back.

Then after all that Guy B hired two people to do the job my husband was doing. Which leads me to question, if he knew the work he was asking for required two people, why not hire someone to help him, instead of firing the person you already have?

So my question is, does my husband have legal right to file a lawsuit against this company?