I remember once going out "in service" as a young teen and someone gave us material critical of the WBTS. I was with an older gentleman, and thought I can't wait to see this horrible material proved wrong. Instead, the conversation was ended and the "apostate material" was disposed of once we got back to the car. I asked something to the effect of why didn't we just prove them wrong? After all if we have the truth then we should be able to show them where it's all wrong, right? My questions were blown off, and that never sat well with me.
So apostate talk can work sometimes. That probably raised the first doubts I had, but I didn't fade for years afterwards, and ended up getting baptized anyway. So, maybe it just took a few years for it to work... or something.