If they don't have the problem solving abilities to stop a fat kid from picking on them, they probably won't function well in the real world anyways. God knows what will happen when they're faced with real adversity.
Anyways, it seems to me you're just venting your own personal issues.
Whether it be you or any other kid out there, all children should know that a bit of playground hooliganism is just par for the course compared to what really happens out in the real world. People kill other people,
people get diseases and they die. People live on streets. People don't eat. People work for dicks. Good people never get what they deserve. Professionally or personally. I'd rather put up with (or be forced to try and handle) a bully than face those circumstances any day of the week. But that's life after high school.
As a great vocalist once said, 'the world is a vampire'
Get used to it.