Locked-up troublemakers still make trouble though, don't they? Their very existence signals to those not locked up yet that there is something wrong. That you c

Locked-up troublemakers still make trouble though, don't they? Their very existence signals to those not locked up yet that there is something wrong. That you can be punished for having ideas and behaving in ways they don't want. They are many things at that point. A source of inspiration, a lesson in how to maybe not be locked up yourself. A target for rebels to rescue (that would be embarrassing). Getting more extreme doesn't fix it... if you simply execute them, then they're martyrs. It can't be fixed later (like with prisoners, potentially). You don't get to un-martyr them. The question is how you erase them from existence itself. And the totalitarians have started to figure out the solution to that problem in the 21st century, I fear.