I don't quite understand the "injustice". If the rules of the group require a certain GPA and you didn't achieve it, then you can't join. The rule might be a bad one but it doesn't seem like anyone did something bad to you. You seem to value education for its own rewards-you took classes that you found a challenge and you love music-why does joining that group mean so much to you? Joining or not will have little effect on your career or life, so why care?