Communism

Are you referring to the soviet prisons in general as "re-education camps?" An enormous number of prison deaths occured during World War II, when famine was widespread due to the Nazis storming Ukraine, the USSR's breadbasket. On the whole, soviet prisons and the justice system itself were more progressive than their peers, Mary Stevenson Callcott documented it quite well in Russian Justice.

The soviet union, despite having a progressive legal system, was in a state of constant turmoil caused by pressures both external and internal. They couldn't simply delete all previously existing ruling-class people and ideology, class struggle continues under socialism. Further, pressure from the imperialist west, invasion both in threat and in action, and intentional sabateurs meant that the prisons certainly weren't empty. The soviet union never had a single year of normal, stable growth, free from intense opposition on the outside and counter-revolutionary forces on the inside.

I'll state it again, as I said in my other comment: the red scare existed because porkie was terrified of a system that stood to steal from under their feet the very foundation they set up for their total reign.