Do you really believe Stalin would have been a good person (or at least neutral) rather than an evil SOB if he hadn't been exposed to the theory of evolution?
I guess he would have been restrained by a fear of Hell, from doing the evil he ended up doing. I think a person can be led to Hel; that one can take a young person, expose him to all sorts of vile ideas and succeed in corrupting him entirely.
Could he have ended up as a good person?
Maybe.
Reverend Jim Jones make you suspicious of the ideas of Christianity or organized religion?
No. Jones can be shown to have perverted Christ's teachings by comparing his deeds with what Christ commanded. Stalin cannot be shown to have perverted Darwin's teachings -- at least in moral sense. Note, that I'm not claiming Darwin would advocate Stalin's actions.
Or do you agree with me that evil SOBs will adopt/pervert any convenient argument to serve their evil purposes?
Yes. But is everybody who does evil born without the capability to do good?.
And if so, do you concede that it's possible Stalin declined to follow Christ's teachings because it would have cramped his evil SOB style, rather than because Darwin convinced him to do so?
It's possible. Do think it is possible that he would not have done the evil he did, if he had never been exposed to Darwin?
I'm not aware that Darwin made any moral teachings. The study of science (or geometry, or music, or dentistry) is not the study of morality. So of course Stalin didn't pervert Darwin's moral teachings, because he couldn't pervert that which doesn't exist.
As for the study of evolution being the cause of Stalin's loss of faith (if he ever had any), this means very little. Many people fall away from their faith. Sometimes it's because they suffer a loss they can't accept, or because the preacher turns out to be a scoundrel, or they experience a plain old "crisis of faith." These things happen. Such people don't automatically go on to be mass murderers. Reading Darwin (as millions of people have done with no ill effects) obviously doesn't turn someone into a monster like Stalin. If it did, we'd have millions of Stalins running around.