Only one thing to add to that: his voice must be heavily controlled. Not taken away of course, but he must not be allowed to pontificate to his drooling followers. He's never been shy about embracing stochastic terror while a free man; imagine his behavior when he has less to lose.
The only people (other than fellow inmates) listening to him should be the prison guards. And when he complains that he's being treated unfairly with his uncomfy bed or whatever, they can silently gesture to all the identical cells around him for the hundredth time.
Maybe when he's lost the one thing that gives him a sense of power he'll be forced to attempt some kind of introspection, and hopefully find the tiniest kernel of empathy.
Or I can just wake up from my daydreaming.