And? The Bolsheviks and the Mensheviks were both socialist factions who were coming from the same intellectual milieu, and they killed each other.
Perhaps the author of the article is a rationalist, too. He certainly knows too much about them, cares too much, and the fact that he criticizes them only shows that there is some infighting among them.
Well it's a good thing I only mentioned the two groups who were explicitly socialists!