If he was sitting minding his own business and behaving himself, my feeling is he should have been served. I feel for the restaurant potentially losing business if OTHER patrons decide to exit stage left on seeing him there.
But I'm uncomfortable with the idea of people being refused service just because staff don't happen to like their views. I hold some pretty strong GC views - should I asked be asked to leave a restaurant because of them (granted I'm not a public figure)? Should someone who holds TWAW views be asked to leave if the staff don't happen to agree?
They're there to serve food, not stand in judgement of someone's political views. If the staff felt he posed some sort of threat to their safety (which is possible given his record), that's a different matter.