Agreed. Story from my own experience... my dad once sent me to a religious retreat and I was totally eating it up. In hind sight I think it was just a convenient break for him. I approached him afterwards and told him how much I was feeling it. It had reinforced my beliefs strongly at the time. He then looked at me and said, "yeah, it's all brain washing". The whole weekend shattered then and there as I realized he was right. It wasn't critical thinking that made me realize it was all shit, but by taking apart what they were doing to me and how it was distorting my perspective.

You combat this type delusion not with facts but in snapping a person to their senses as to how nonsensical their position is. Make them realize it themselves by pointing out small flaws in the method, not the message, and let the victim put it back together. There are kernels of truth in religious doctrine, but it's usually covered in shit for some assholes agenda so it can be hard to just let go.