He doesn't usually feel guilty about things where people can see them - it's such a self-centered emotion, it's almost never the best thing for another person to interact with (he is thinking of this as agreeing with Leareth, not paying very much attention to the distinction between 'does more than is helpful' and 'is there to be interacted with more than is helpful', because that'd be an in-depth conversation that should wait)
- but pulling any emotions away from where Leareth can see them feels like it might break the trust, here.
It does not seem all right that Leareth feels helpless but there are not a lot of ways around it while it remains objectively stupid to give him all his magic back, which it does. Sometimes prisoners seem all right for a while and then kill everyone around them and he doesn't have a working model of when and why enough to guess whether they're past the point where that might happen or not - and if the risk were actually literally just characterized as 'Leareth might kill everyone around him' then that'd be fine, really, at least while Vanyel's not around, a good trade for Leareth feeling less helpless, but probably he should not conclude that that's the only possible bad thing.
Still, he could try to do some problem-solving about Leareth feeling helpless. He could...give him a knife, in principle, that follows from being fine with Leareth killing everyone around him but not with anything more complicated, except it would clearly be an injustice to Leareth to let him kill himself right now, not that he seems inclined to, but better to be safe - once Vanyel's back they can get the Mindhealer to unblock some Gifts, at least the ones Leareth uses to read people and shield himself -