I don't think anyone's trying to argue a strict equivalence between Japanese internment and the Holocaust or the Rape of Nanking. We can identify injustices without forcing them to meet the standards of history's greatest atrocities, especially if we want to pretend that we hold ourselves to higher standards.

That said, it's chilling to wonder what would have happened if command had ordered the mass execution of the imprisoned. Would the military have had the integrity to refuse the command? I can't imagine that it would have been impossible to find friends or family of the thousands of Pearl Harbor victims who would have been willing to carry out such an order.