If that's the point of the article, then its a pretty terribly argued article.

If the author wants to argue that we have less intellectual diversity now and its bad, finding some examples of ideologies that don't want to mass murder specific ethnic groups would go a long way to making the argument convincing.

[And i'm starting from a place where i believe intellectual diversity is a good thing, although i think we have more now than we did in the past. Its not like i disagree with the author on that point, I just don't think s/he actually cares about intellectual diversity and instead just likes nazis. ]