There was no "wrong." He was a homo. The Marines forbade homos from serving. When they found out he was a homo, they discharged him, and since he had lied about being a butt pirate, the discharge was dishonorable. As it should have been.
The only ones "wronged" here are the Marines, who have been portrayed as the bad guys while the rump wrecker is a poor, unfortunate "victim."
Hogwash.
Most likely, the Marines found out when he was arrested for Solicitation or was caught trying to molest a lower rank.
NY Times foodie Craig Claibourne served in the Navy in WW2 and Korea and he said homosexuality was more accepted in the service as long as you kept quiet about it. Especially if your steady lover had a wife.