I don't know if we really know the facts in this incident to make a proper judgment. We know that Bird was treated in a hospital, so he must have been injured. We don't know much about his girlfriend, though it sounds like she was injured, too. The stuff about being dragged around the apartment, etc.. would need verification.
The media tends to rush to judgment in these cases without knowing the facts, so the public forms an early view which may or may not be accurate.
I would like to know what really happened before I make any judgment. As for the Celtics, unfortunately they are more beholden to the media and public relations. And so more influenced by news stories.
My impression is that in most of these high profile domestic incidents, the male is usually the target of the blame. That may be the case here, but the facts need to be known.