Although I, too, refrain from debating with Jehovah's Witnesses when they come to the door (and they don't seem to visit in my village now), I see things slightly from the other side as my sister converted to Mormonism a while back. Whilst I don't agree with her beliefs at all and find some of what goes on within Mormonism very very troubling, she seems really happy now and it appears to suit her right down to the ground. She's a very intelligent lady who used to volunteer for an organisation that rescues people from cults, including the Mormons. She knows all about the weirder aspects of their beliefs but has still decided to choose to believe them now.
It's a bit mind-boggling to me, but I can't help but think she's happier these days with her Mormon faith, new Mormon husband, etc. She has many non-Mormon friends and still seems pretty sensible about most things - she'll serve me a cup of tea when I go round.
I do think that those who say people of any faith 'believe in the white-bearded man in the sky' or 'talk to imaginary people' are being a bit unfair; clearly there's far more to religion than that, there is some evidence for the existence of God (although many of you of course don't find that evidence compelling) and it's not a sign of lack of brains if you believe.