I’m sorry this has happened to you. I see these types of personalities in many gyms I visit, but I pay no attention to them. Unfortunately gyms are the gathering place for many of them, because that is how they feed their egos.
Have you tried to bring this issue to the gym manager/owner attention? It would be cheaper and more effective than a lawyer (unless bodily injury has been done to you). Usually that helps and they can have them remove from their facility and revoke their memberships. The last thing gym owners and managers want is negative publicity and attention for their businesses. Good luck to you!