why didn't rudy's parents want him to go with the coat men?

Rudy is eavesdropping on the "coat men" who are quietly talking to Rudy's parents in the kitchen. The Nazi agents want Rudy to join a special school because of the three gold medals that he won at the Hitler Youth Carnival. The men want to take Rudy away to a special military school that will develop his athletics. Rudy's parents refuse to let him go. They did not want him to leave home and join the Nazis. Later on his father is arrested because of this.