I think you'll find literally no-one is condoning the Port supporter's actions. However, it is possible for both parties to be in the wrong. In my opinion the Port supporters shouldn't have been harassing Clarkson like that, but Clarkson was also wrong to react in the way he did.
Clarkson tried to walk away - three times. The dickhead wouldn't leave him alone. The idiot had his chance to back off and he didn't.