To me, this is where he goes horribly wrong (beside just generally being poorly written). This is only a true statement in a specific sense of the word "best", one that we don't normally use. In evolutionary terms "best" might be taken to mean an attribute that ascribes the greatest chance of passing on one's genes. When talking about ideas, one would hardly say that the ideas that are repeated most often are the "best". Is Brittany Spears a better artist than Tom Waits because she has sold more records? Maybe to an Ayn Rand disciple, but I think to most people probably not.

Ideas certainly evolve, but not in a qualitatively similar way to organisms. Organisms change by random variation, which sometimes leads to a higher chance of survival, but only if the change allows an organism to more ably fit into a niche. Ideas don't randomly change; they change in specific, purpose-driven ways, and can survive even if they are terrible in many instances (by the logic presented by the author, killing Jews was the best among the competing ideas in Weimar Germany).