Good for him. I don't care. People have been fired for dumber reasons. If you think you are going to go to work and ignore your boss's instructions without consequence, then you probably are not smart enough to hold a job in the first place.
as many have said--it's a completely legitimate contention that his tie was driving away customers. To say "customers didn't mind" doesn't acknowledge that customers may not have interacted with him and been turned off by the tie. As many of us know, sports passions can run deep.. I don't think it would have affected sales. But it's certainly within the realm of possibility. For the salesman to ignore his manager's request is idiotic when faced with the consequence of losing his job. I hope he gets no more publicity and really hope he doesn't win any kind of settlement $$
Here's another question. If the Rockets get beat in the WC finals by the Mavericks and you were looking to buy a new car the next day and you went to a dealership with a salesman wearing a Mavericks' tie would you want to buy a car from him?