If this whole scenario happened on the street -- with ordinary people -- gunning the engine would demonstrate bad intent in front of any jury, regardless of why or in what manner the pedestrian walked into traffic.
The way these cars handle, he could have been gunning the engine to avoid the kid, or to scare the kid and give him a face full of dirt. These are not street cars.
With that being said Tony Stewart is one of the few drivers I believe to be arrogant and reckless enough to risk gunning it for laughs without regard to the possible consequences. See post 270.