The soviets didn't really care who they killed. At one point they had quotas for how many people to shoot. Without the incentive of profit, they had to have the incentive of not getting shot in the head. It didn't matter so much if they people where actually guilty of anything, that was just a bonus.

The nazis were pretty anal retentive about killing the "right" people, hence all the sorting with IBM punched card machines and SS companies capturing and analyzing census data.