Excellent point, Mozzie. In their mind the only ones who leave "the truth" are those who are seduced by the world, fall prey to immorality or lose their faith in God. The one elder who has spoken to me since I found the exit door broadly hinted that he thought I was being swallowed up by materialism. Between them they don't consider any of them count or warrant further thought and back that up with an out-of-context use of a scripture that says "They went out from us, but they were not of our sort."
The fact that those leaving make up such a big slice of their congregation seems to escape their notice, so they gleefully point out the failure of other religions to keep their flock.