That's odd. Stalin, the biggest leftist of them all, murdered his Darwinian evolutionists. Trofim Denisovich Lysenko. Stalin's biologist, definitely an anti-Darwinian.
And if you're correct, then how can you explain this article from the Institute for Creation Research? Darwin's Influence on Ruthless Laissez Faire Capitalism. ICR links Darwin to good ol' capitalism.
Stalin & Lysenko believed in a different variation of evolution, essentially Lamarckism. They believed creatures evolved not through random accumulated mutations in life forms, but through physical action by the creatures themselves. Below is a passage from the link you provided:
#####According to Lamarck, evolution occurs because organisms can inherit traits which have been acquired by their ancestors. For example, giraffes find themselves in a changing environment in which they can only survive by eating leaves high up on trees. So, they stretch their necks to reach the leaves and this stretching and the desire to stretch gets passed on to later generations. As a result, a species of animal which originally had short necks evolved into a species with long necks.#####
So, the Stalinists believed in a different version of evolution that the Darwinists. They also believed in a different form of communism than the Maoists.
As for the ICR link you provided, if you read it thoroughly, you'll see it's referring to natural selection, not evolution. I have no problem with natural selection, and agree that it can exist quite comfortably with good ol' capitalism. Natural selection is not evolution.
Ruthless placemarker