The video makes me blame the other guy 100%. What idiot gets out of his cart, walks out onto a track, and tries to confront another driver? If someone did this on the 101, we'd think they were delusional!
The throttle from the video I saw has already been dismissed as coming from another vehicle closer to the camera.
Stewart looks like he was behind another car that avoided the pedestrian at the last moment. Probably didn't have a ton of time to react. Looks like he "fishtailed" a little and maybe hooked the guy with the rear of his car?
Not a good situation. I am now Tony Stewart fan, but I can't blame him one bit. The other guy played chicken with racing vehicles on a dirt track and lost.