I'm new here, so I hope I don't offend anyone with my opinion, but since you asked...
The circle track guys play way to rough to begin with. This is supposed to be "racing", not bumper cars. You're supposed to give the other guy room, not stuff him into the wall like that. The things circle track guys do, would never be allowed in F1.
Tony Stewart is a special kind of idiot. He's already run over 2 pit crew, causing serious injuries. When you're in a car, and someone else is on foot, you have to take special care not to injure that person. Yes, you are your brother's keeper. You didn't see Matt try to run over Tony, after Tony threw his helmet.
Having said that, I feel really sorry for Tony Stewart right now. This guilt will be with him for the rest of his life. He may have finally learned a lesson, but way too late.