Ernesto Che Guevara said this quote

“ When asked whether or not we are Marxists, our position is the same as that of a physicist, when asked if he is a “Newtonian” or of a biologist when asked if he is a “Pasteurian.”There are truths so evident, so much a part of the peoples’ knowledge, that it is now useless to debate them. One should be a “Marxist” with the same naturalness with which one is a “Newtonian” in physics or a “Pasteurian.” If new facts bring about new concepts, the latter will never take away that portion of truth possessed by those that have come before.Such is the case, for example, of “Einsteinian” relativity or of Planck’s quantum theory in relation to Newton’s discoveries. They take absolutely nothing away from the greatness of the learned Englishman. Thanks to Newton, physics was able to advance until it achieved new concepts of space. The learned Englishman was the necessary stepping-stone for that.Obviously, one can point to certain mistakes of Marx, as a thinker and as an investigator of the social doctrines and of the capitalist system in which he lived. We Latin Americans, for example, cannot agree with his interpretation of Bolivar, or with his and Engels’ analysis of the Mexicans, which accepted as fact certain theories of race or nationality that are unacceptable today.But the great men who discover brilliant truths live on despite their small faults and these faults serve only to show us they were human. That is to say, they were human beings who could make mistakes, even given the high level of consciousness achieved by these giants of human thought.This is why we recognize the essential truths of Marxism as part of humanity’s body of cultural and scientific knowledge. We accept it with the naturalness of something that requires no further argument. ”