Banks freeze accounts under the effective duress and cover of the government, because freezing money is stealing money from someone, even if you (might) give it back one day. If they didn't have the cover of the government then they would be under a ton of liability.

Much like how taking someone's car, even if you plan to give it back one day, maybe, if you think they deserve it, is still theft.

Because banks do it under duress, it's really the government that is doing this, not the bank itself.