The overreaction I'm talking about is when two kids simply get into a spat. My sons (twins) were small. I do not know where they got it from but they would simply not put up with a slight. My son Josh would often times get into a fight. I have to say, it was rare that he started it. He wasn't aggressive. He didn't bully kids. He just wouldn't take a offensive from anyone. I was called more than once to his school and told that I needed to take him for counseling. Maybe he needed to see if he had ADHD or something. It was an overreaction.
THere was nothing wrong with him, he just wouldn't be talked down to. He rarely was suspended because it was never him that started it. I would use the same arguement you are using. "Is he not allowed to defend himself"? He knew I would be pissed if he was picking on someone else. It happened one time and I wasn't happy. I personally called the kids mom and apologized. They are good friends today. Josh has stuck up for him more than a few times. (he's someone that was often picked on).
He is 21 now. 5'9 and about 128 lbs. Nobody in the area messes with him. LOL I believe that most bullies don't want to actually fight. Everyone knew that Josh was happy to punch you in the nose. At 18 he said he wanted to fight in the local Toughman contest. That year the lowest weight class was 139-158. He weighted 125. I bought him ankle weights to weight in. He made it to the semi finals.
I do not have a problem with kids fighting. What I taught my kids was that the answer was not to fight BUT if you had to, then you had to. His brother is the same. Over the years they have beat the crap out of each other. LOL Justin got his butt kicked the year before last but he wouldn't quit. The ringman told him to not go out for the last round and he said he was fine. Got beat bad but he went the distance. I'm pretty sure that Justin has never thrown the first punch ever. Swing at him though and he will never stop hitting back.
The reason for my story is that even though they were always small, they never, ever allowed anyone to bully them. I was fine with that but I never encouraged them to fight.
I realize that some kids are different. I would never punish a kid for fighting back.