As the tallest kid in my class from first grade on up to graduation, I had to put up with a rabid chihuahua on occasion, you know, the "little guy" syndrome. I discovered early on that it didn't matter if you were defending yourself or not, the people in "higher up" positions, namely principals, teachers, superintendents, etc looked down on the larger of the two people involved because he didn't just walk away instead of pounding the "poor little kid" into the ground. Add extra punishment if the kids' parents were influential in the community.
Not liking the punishment that came, I rarely fought back, most of the time I just chose to bide my time and wait...sometimes smashing their appendages in lockers, car doors, or a geography book upside the head, I saved the kicking them in the crotch for the real #$%*s, you know: Jocks, or REAL tough kids who could kick my ass if I didn't use that tactic. The satisfaction that comes from busting a Jock's cup into pieces while he wears it, with a steel toed boot is priceless, especially if done in front of his girl friend or fan club. The reason bullying is running rampant is because people have been conditioned to just accept whatever the wannabe alphas dish out...
Unfortunately, in society, we have to suffer the consequences even if it's self defense...personally, I don't think this Casey did anything wrong. He didn't keep kicking the kid when he was down, although the bully probably deserved it. I commend the young man for not stomping the bully's worm-eaten brain out in front of the other kids.