I agree that firing should be considered in this case, but I'd have to consider discussing the situation in a case like this. Unless Domino's has a "one strike" and you're out policy, I would hope a situation like this could be discussed. Then again, many corporations don't use common sense.
It was the patriotic fellow who hadn't used common sense. He admitted to being overwhelmed emotionally after watching a TV account of the war, and that he didn't know what he was going to say when he got to the stranger's door. These are not hallmarks of common sense. If the roles were reversed and you had some worker from a pizza company knocking on your door wearing his uniform and proceeded to harangue you about flying your American flag and how evil the President is, I would wager you would be calling his employer, too, to complain.
Because they deal with the public, they are more than likely subject to certain rules of behavior off the job when it comes to besmirching the integrity and reputation of the company. Attending an anti-war march with a Dominos uniform on might result in a similar termination.