Terrorist prevention centers. That doesn't sound hideously scary does it?
With that name you can just about justify anything you do within them. There are not prisons. They have religious freedom. We just have to do whatever is necessary to prevent them from hurting other people. For their own good and the good of others.
This is the road that Socialism ALWAYS goes down. Leftism even in the US is just the preamble to Socialism. But Socialism always enslaves people. The USSR was considered by those living within it to be a large open air prison.
Once 1 person or 1 committee gets to make decisions for society, that entity's view point and preferences is turned into a plan. More directly called a set of laws. These laws are made in order for the proper functioning of society. If individuals do not abide by these laws they are threatening the operation of society at large. Dissidents can not be aloud to speak or disobey, because the fate of the whole society is in question. Once your society elects to be Socialist, this is the reality of the situation.
Read Hayek's The Road To Serfdom. It is a much better explanation of what I just wrote.