I think you're missing the point.
Stalin had a lot of Marxist/Leninists killed, too. That means Stalin was not guided by Marx and Lenin?
According to Yaroslavsky -- a Stalin sycophant -- Stalin credits "Origin of the Species" with inspiring him to abandon Christ.
The difference is that the darwinists were executed for being darwinists. The marxists/leninists were executed for being in the way (power struggle) rather than to achieve ideological purity. This kind of thing happens when scientific work become subordinate to the government.