Dear PH, IMHO, you really do need to get past the "sloganeering" and look at the facts. That little motto of Marx has the sole purpose of proselytizing people into Marx's "new dispensation" for the world. The uncooperative are subject to Marxian "selection" -- in the negative sense.
Marx has to "correct" the world, because he detests the way it has evolved and is evolving: He finds it senseless -- which is all that Darwinist evolutionary theory makes it to be.
What we are looking for here to clarify the point of Marx's awareness of Darwinist (and Spencerian) evolutionary theory is to be found in Das Kapital. I'll try to get my hands on a copy soon, and track down a cite or two for you.
Thanks for writing!
Here ya go, BB: Here's an online version of Das Kapital.