The problem with people who have strong convictions is that they often have a simplistic, polarized view of everything that allow neither subtlety, nuance nor meaningful discussion.

Usually it's pointless and frustrating to talk to such people because you know they're not trying to share ideas, nor are they open to questioning their own beliefs, but rather they're just telling you how things are and never listen to you.

Exactly like religious people in fact - which I avoid like the plague also, for the same reason.