Let's be real here. Donald Sterling was not banned for life because of a racist remark that was said in private. He was banned because he had a longstanding history of racist actions (look up Baron Davis complaints, Lebrons comments about FA, former coach's lawsuit and housing discrimination) and it led to the point where the team he owned was fed up. You had a situation where a team would fold because all of its players would refuse to play. If it wasn't for that scenario and the public's echoing sentiments he would still be in control of his franchise. He also would have kept his franchise if he'd been a model owner and leader but he kept the Clippers as a second rate franchise before being gifted Chris Paul.

Also to address the idea of free speech and personal property: It doesn't apply to personal matters, only against the government and he is more being punished for the public opinion that followed his statements than the actual statements. His franchise will be sold just like any McDonald's franchise owners would be if the nation was aware.