Who am I to screw up their happiness?
If it wasn't for the shunning and blood doctrine, I couldn't have cared less about what Jehovah's Witnesses believe. They could have believed in lizard aliens in human skins that rule the world. If the belief made them happy, good for them. I would only become concerned if they decided that it was imperative to eliminate those "lizard aliens in human skins". My point is that I don't care what Jehovah's Witnesses believe, but I do care about certain actions caused by their beliefs.
After reading the responses in this thread I have added one more reason. It has been pointed out that Jehovah's Witnesses don't give other people the same consideration regarding their happiness. So when Jehovah's Witnesses decided that their doctrine had to be spread worldwide, their ideas became open to debate and criticism .