Communism is the greatest form of human slavery the world has ever seen- David O. McKay. P.S. why are there Karl Marx quotes on a website titled "Liberty Quote"? Waffler: Karl Marx didn't directly kill any one that I can find-but his totalitarian ideas inspired the Soviets to kill those who didn't agree with them, the death toll in the tens of millions. by taking religion out of the system, morality expired behind the iron curtain.