Go ahead and let him serve. Obviously his ideology is just a fashion statement and has nothing to do with the way he lives his life, if he went to damn West Point.
FWIW Rapone is an active DSA member. His Twitter is currently locked but you can read his (Very good) Medium post on white supremacy at West Point.
I'm really not sure why he chose to join the military if those are his political views. I mean, it's his choice and I strongly disagree with an ideology test for military recruits, but I just don't understand his motivations.
Commies love military shtick, too. They are not pacifists.