Talk about over-reaction, this is a perfect example. Sports is to be enjoyed. It is one thing to cheer your team to success and another to be punished for supporting one team over another. This action of being fired for being a supporter of a team is nothing short of uncivil. I figure the owner of the dealership is a Democrat.

This was a pissing contest and the employee lost. Considering the importance of the game, the employee should've brought along a backup tie just in case he was told to remove the offending tie. It's called common sense. He could've put his original tie on once he was no longer on the clock.
Keep in mind this man is in sales and when you are in sales you have to keep your customers in mind as well as any sponsors you may have. So the employee was not only playing around with his own money, he was playing around with the owner's money also.
For all we know, there could've been a clause in the paperwork between the dealership and the sponsoring team that prohibit all/any employee promoting or endorsing any other team during this union.