Why do liberals adore some socialist murders, but not others?

I've graduated from college, so I've seen the idiots with the red Che t-shirts. I know many liberals love him, along with Castro, Lenin, and Mao. But where is the love for Stalin? How come I don't see liberals with Stalin t-shirts? He was a socialist, an atheist, and certainly murdered enough people to deserve the respect and admiration of liberals. So, why do liberals love Mao, Che, Castro, etc, but not the Man of Steel? Serious question for liberals. I really want to know why some murders are considered cool, while others are ignored.