Yep, saw this earlier. I'm not a big fan of racing, though I suppose that dirt racing they were doing looks more fun and interesting than your average NASCAR race. Though when I was reading this earlier, it was brought up how Tony Stewart is known in the sport for his anger and has always been associated with being a dickhead.
Now, with that said I (and others) don't think he purposely tried to hit the man. Did he have a malicious intent, given his history of being a total douche bag, attempt to 'scare' the other driver by driving too close to him or trying to hit him with mud and debris? Probably. And of course, even if it was an accident, if his intent was to 'scare' him by doing something like that... then well, that's not going to be good for Tony.
And yeah, don't get out of your car on a poorly lit night track when people are racing to express your disagreement with another driver. You shouldn't do it on the freeway and shouldn't do it on a race track...
EDIT: Fun fact, I was just in Tony Stewart's hometown of Columbus, Indiana this weekend as I had to travel through it to get to and get back from a wedding. They proudly display "Hometown of Tony Stewart" on signs...