@mehdi132
When you join a sports club you have to keep your hair closely cut. It's supposed to promote unity by making everyone equal with looks and foster a sense of shared tribulation. Also helps with keeping cool.
Everyone gets a hair cut, everyone works for the same goal, everyone is part of the team.
"There is no 'I' in 'team'.", taken to the maximum basically.
The older brother was bullied into joining the Judo Club, and lost his individuality at that moment. It's not a big deal to people who do it willingly but to someone who isn't I can imagine the sense of loss would be a great shock.