I am in a situation where my PC's are captured and being interrogated. This isnt a harsh thing, acctually its just a guy talking in plain truths. The persont they tried to kill, thinking he was some super evil guy is realy a chaotic neutral leader of a somewhat shady smaller organization that is affiliated with a larger, more evil organization.

The PC's are acting like zealots while chained to a table. The NPC now views them as lunatics that are hell bent on killing him. I have given them a few chances to try to change things around and talk the NPC into letting them free, but the continue to dig a deeper hole.

Now this NPC feels that if he were to let them free for any reason, he would be a fool as they would almost certainly try to kill him. He already knows they are very able fighters.

I never planned this encounter to be life threatening. The NPC's charisma was supposed to make the the PC's talk to the guy and learn some valuable information. But the PC's chose to attack him the moment they saw him.

What should I do?
The NPC should have killed them a while ago.