Though of course, faith plus ancient texts which condone violence can be more dangerous

That means you can actually make people less harmful if you tell them to listen to their hearts instead of listening to ancient texts. The person who's completely in their head and analyses the ancient text for absolute guidance of action is dangerous.

A lot of religions also have tricks were the believer has to go through painful exercises. Just look at a Christian sect like Opus Dei with cilices. The kind of religious believer who wears a cilice loses touch with his heart. Getting someone who's in the habit of causing his own body pain with a cilice to harm other people is easier.