I think I would've probably tolerated the religion if "conscience" really did play a role in the religion. There are many people in religions that do not believe EVERY thing that is taught, yet they are still members in good standing. Of course, Jehovah's Witnesses aren't like that.
You HAVE to believe it all or you will be "no longer considered a Jehovah's Witness". That designation means you cannot be talked to, you will be shunned, etc.
But if the religion wasn't so extreme, I bet many would still be members. What do you think?