Of course he was angry. People were being experimented on and everything around them told a story of possibly violence against a vulnerable innocent. He was livid. At their captors, at himself for not being more vigilant. At this person for being so daft as to not realize the grave situation they were in.
And that was not a defense. The fact that they didn't know what happened to Drina and her baby, that they didn't know what had been done to Eden and the Scots girl, were exactly the problem. And since these people had kidnapped the, ripped them away from their lives for an unknown purpose, he was wagering what had happened to Drina had been unspeakable.
Luckily, the idiot did have the sense to back off and stop saying such stupid things. Cathair let him go. He had better things to do than try to make this one see the reality before them.