He is dumb for not changing his mind in the face of new evidence/logic.
"Everything is relative" Is already contradictory on itself. lt is saying "there is no statement 100% correct" or "I am lying now".
He was put in a corner where either he admits he would rape a child if certain circumstances are met, that he would commit mass genocide under certain conditions... Which he obviously wouldn't, as I assume he is a normal person.
But since he refused to change his mind, I'm left with two options: either he is dumb and want to keep blatantly wrong ideas or he is mentally ill and actually believe those ideas and would actually do those things.