Mission- I'm not a Jehovah's Witness, and I don't agree with their stance, in fact I'm not religious myself at all. I do try to understand why religious people make decisions that are counter-intuitive to me. What I said above is the closest I can come to that.
Similar to yourself, in the new-born baby situation, I would act as you would- defend the baby. But people can and do act otherwise. Whilst I don't agree with that, I do want to understand it.
I'm sure my characterization is not accurate, and I'm also sure, as Errol mentions, that it's not as simple as that. With all organized religion, there are structural influences, the presence of elites and in-group/out-group dynamics.
But equally, I do see that religion does cause people to think, act and feel differently. It does create senses of purpose that can move mountains. I don't think all religious people are simply duped idiots, I do see it adds something to their lives, and the lives of those around them, and I am intrigued by that.
It might be that religion is a useful fiction. Or it might function, in some instances, to remind people of their own fallibility, that there is a limit to what human reason and emotion can achieve at any given point in time.
I think there is something useful in examining religious difference (particularly the differences between those who are religious and those who aren't). It is a big part of our human history.