I've only ever heard of one mormon who converted, that being one of the members here. But I guess there must be more otherwise they wouldn't put so much emphasis on missionary work.
Bottom line is, to an adult who's belief system is well developed other belief systems appear irrational. To an immature person who's belief systems are flawed or incomplete, mormonism may offer an answer. As could any religion. Or even atheism.
Personally I made the conscious decision to eschew religious belief and come up with my own conclusions, which eventually led me to Deism; but I can understand the draw of religion. If I just sacrificed a considerable portion of my logic, I could have had all the answers I wish all justified by divine authority. Would have simplified my life greatly, and provided a comforting emotional fallback and a large social group to immerse myself in. I even tried a few times, in my own way. What always brought me back to Agnosticism and later Deism was my morals, I couldn't be part of a religion and look myself in the eye. I'd always feel like a liar, lying to myself for the sake of comfort. That was and is unacceptable to me, but some people are willing to take a little ignorance with their bliss.
Note that "bliss" is more complicated than you might think. I've heard many religious people describe their conversion as painful as they atoned for their sins or whatever, but that's nonsense IMO. They aren't in real "pain", they're just feeling pain because it's the cost of validation, which they enjoy.
But regardless, there's no reason to disrespect someone for any of the above. Calling them stupid (as Neckbeard does) merely displays ones own ignorance and insecurity. They are people like any other, there is no "master race" of atheists out there. In fact I've known many atheists who are more insecure and incapable then their religious counterparts. Sure maybe the atheists are more intellectually honest, but who's the better person? The religious conservative with a strong family and career, or the insecure atheist who lives in his mom's basement? Or vice-versa? You have to take people individually to render an accurate judgment, and Neckbeard/HAL's eschewing of this basic logic actually shows his true colors. He says his belief system is based on logic, but makes the most illogical and overgeneralized assertions, that even the basic, raw science of psychology and statistics says is wrong. If he published a logical, scientific paper on that premise it would be laughed at by some of the most logical people in the world. This reveals a flaw in his belief system, but instead of turning to religion for validation he seeks it by putting down others.
A mature adult of any belief system is already validated by whatever beliefs they hold; and while they may debate religion, even passionately, they never stoop to the sheer immature irrationality by calling an entire group of people "stupid" with no logical support.