As a parent, no, I would not be okay with my child being shown graphic images such as that. True, you'd see images just as bad in a rated R horror movie, but that's why you need to be 18 and older to watch them. I hope my children don't want to watch that kind of stuff when they are older anyways.
It doesn't sound to me like any of those images had anything to do with driving, especially the burning people.
You can see gruesome images on regular television shows (Bones, CSI, Criminal Minds, etc) well as PG-13 movies.
In High school we saw many gruesome images from car accidents and from STDs. Think about this, the burn victim could have been burnt by an arsonist that could have been a teen or could have been a victim of a drunk driver. In Kentucky in 1988, a tragic bus crash left many victims dead or burnt. These victims were children who have had to live with their scars through these years. Unfortunately burns and other graphic/gruesome events happen in life.
If a Junior cannot handle those graphic pictures than what are they going to do if they are ever confronted with those injuries in real life??