I understand your frustration. And, unfortunately, if he's going to school.. this will cause him problems.
Kids torment the kids who make it fun. Even as babies and toddlers, they will pick on the kid who cries easily.
I had a daycare boy who at the age of five, cried when a nine month old hit him on the leg. So, she hit him again. It didn't hurt him... but, it made him cry. We worked hard with him. We tried everything we could to help him learn more appropriate ways to deal with his emotions. We stuck up for him when it was reasonable. But, sometimes, he was being completely unreasonable and just crying for lack of a better way to deal.
He got to kindergarten, and cried every time someone offended him. But, he spent so much time crying, that eventually the teacher stopped listening. The few times he had a really good reason for his distress, nobody listened because it was just one more crying jag.
He's going into fourth grade, and he has a better handle on things now. He still gets very upset, he still gets tormented a little... but, it's mostly normal every day events that bother him more than it would other kids. He still takes everything very seriously. He has no sense of humor. If you've ever seen "Big Bang Theory" on TV... he's SHELDON.
But, with time, and lots of explaining, he's learned to keep it together until he gets in mom's car, then he has one big day's worth of meltdowns. He's incredibly bright and sensitive. He's always had a really strong sense of right and wrong. He can understand how others are feeling, and he's always the one to reach out to another child.