"Even if I discover that this is not the true religion, I will never walk away, I have invested too much of my life to ever walk away."
That's simply their, albeit inadvertent, way of admitting they are weak-minded people. They have said they would rather a comfortable lie than an uncomfortable truth. There's not much you can say to people who readily admit they want to be lied to.
This attitude is very prevalent among the dubs.