From all the comments, articles, books, etc. I've read from other players -- and from Phil himself -- it's both. As others mentioned, he has the reputation for being everybody's best friend away from the table, he's a "shirt off his back" kind of guy for any friend in need.
I think his antics now have a strategic element to them, but they're borne of a deep seated passion for the game that borders on an obsessive/compulsive disorder. He strives to play a "perfect" game and he expects others to as well, so he has zero patience for bad play, bad calls, suckouts, etc. He gets very emotional and caught up in it all, then blows up, but later he usually apologizes and expresses remorse. I've heard him say that he wishes he wasn't like that but he just can't help himself in the heat of the moment. Impulse takes over. I would not be surprised if there were some mental health or personality disorder type issues at play there, but everyone seems to say he's very well-adjusted away from the table so who knows exactly how much of it is a strategic image thing.
I used to hate him for it, but now I find it both sad and amusing. At the same time, it's also hard to feel too sorry for a multi-millionaire. And as virtually any celebrity PR person will tell you, there is no such thing as bad publicity.