What could they really do if they decide to try and escape?
Like Old One said, no way in hell they make it off the planet.
What would they gain from making trouble? Best case scenario they get put into a real prison again, worst, they starve.
They live in relative freedom and peace. Murderer and rapists they maybe, but they are human after all, why give that up?
They supposedly also found god and we don't know how much elected to stay after serving their sentence because there is nothing better waiting for them out there.
I don't feel it is that illogical at all. Convenient to get the guns out of the game, but not illogical.
As for the guards, nobody forces them to work there. I would assume they have their own demons to work at a place like that. Like Clemens.