Old-school dictatorships were so brash and clumsy the way they punished dissent with firing squads and trips to the gulag. It's just as effective to punish dissent by slowly but surely ruining the life of those who express dissenting opinions. That way, instead of making dissenters into martyrs, you just make them look like losers. Very clever, China.
Actually, the Soviet Gulag was mostly about slave labour - they arrested people to make them slaves because they thought this would be efficient - which it wasn't. If they thought you really were a threat you were executed rather than being sent to a camp. I can recommend Anne Applebaum's book: http://www.anneapplebaum.com/gulag-a-history/
True, but the threat of deportation was nonetheless one of the Nomenklatura's weapon of choice. Someone's death was, even in the aftermath of the WW2 mass carnage, perceived as brutal mean of "solving" problems and could spur further backslash/dissidence. Someone's separation from their social circle however, was a much more safer method and the perpetrators were able to sleep at night because there could hardly be any retribution for such a thing.