Again, My brother and I raced sprint cars all through the 90's. I have driven a sprint car, at speed, on a banked clay surface, on a dusty pit area surface, in the gravel, in the mud, and (much to the chagrin of the Sheriff's department) on paved surfaces. I am VERY familiar with the controls and the visibility with those race cars and can completely put myself in Stewart's position.
Even with a clean tear-off, glare wisps across the plastic shield as you pass under the track lights and you have to operate with faith and familiarity just to get around. Even under yellow, those cars are running about 60 mph until they get lined back up where they go about 35-40 to re-take the green. These cars are direct-drive, they only have an in and out shifter, and must be push-started. Drivers must ease from fast to slow operation and will get on the gas to keep the engine from lugging. You don't want lug a $40,000 alcohol-burning, mechanically fuel injected engine, so drivers will keep them revved to insure a clean burn and proper oil pressure. It is like keeping your car in fifth gear when you slow from freeway speed down to a 45 zone and not being able to downshift. Go too slow and it jerks and bucks on you.
At parade speeds, these cars are extremely difficult to keep straight on the tacky clay surface. The best analogy for somebody to get what I mean, is to compare it to a personal watercraft. Anybody ridden a Seadoo or a Waverunner? No brakes, and you can only turn by getting on the gas. Same damn thing. It is a controlled chaos of sorts.
Like driving in the snow, Stewart was on a trajectory through the corner at about half speed. By the time he saw the kid he would have had to make the only correction his muscle memory would have had and burp the throttle to try and avoid him. But it was too late.
This kid was wearing a black driving suit and was at a place on the track that other drivers would not expect him to be. Safety policies dictate that not even track safety personnel can traverse the racing surface until the red flag, and this kid put himself in harm's way getting out of his car during the yellow. The ONLY place that a sprint car driver is safe on the track is strapped into car with roll bars around them. What this unfortunate driver did was to effectively render himself defenseless by getting out. He paid the ultimate price for it.
Sadness should be the emotion here, not anger.