Ok. If someone kills a person at 16. Should the killer be in prison for life?
Your comparison with murder is ridiculous. First of all, teenage murderers are regularly sentenced to life in prison. A murderer is deprived of fundamental human liberties--Niemann is deprived of being able to compete at the highest competitive level in a tabletop board game, without suspicion.
Maybe in USA. In Europe some countries even have special sentences for young adults (older than 18 less than 21). Here's for Germany:
"The maximum penalty for any crime committed by a person under 18 (or a young adult under 21 who is treated as a juvenile) is 10 years"
(Considering that people become more or less aware about their responsibilities and consequences of their actions at about 15 yo, he is now 4 times the responsible age he was at 16.)
If you believe this, its because you aren't looking. There's tons of explanations online of how it could be possible. Go look at /r/chess.
If you murder somebody at 16, you shouldn't be a free man at 19. Three years is not enough time for somebody to mature and mellow.
Is it entirely fair to the actually repentant? No. But does it keep out the false-repentant? Yes.
It is immoral to close every redemption path to a former sinner.
