I can understand how angry the vet might be at the storeowner. Yet, the vet still acted like an uncouth jerk. He showed no tact or class. He could have simply, politely, asked the storeowner to put the American flag above the Mexican flag, since he is in America. Instead, he seemingly felt the need to put on some kind of violet show for people.
This kind of gutless, pussy, lily livered sniveling don't get SHIT done. There comes a time in everyone's life when they have to stand up like a MAN and DO something RIGHT, regardless of the repercussions. Of course YOU wouldn't know JACK SHIT about that would you?