Saying "yelling at large crowds" is irrational, without giving any definition of "rational," is quite problematic. The author can't mean "rational argument", because the power of the West is not built on Modus Tolens; it's built on guns, smallpox, and better industry. Thus, he does not seem to be using a consistent definition of rational; furthermore, "You won't conquer the world by reasoning with people" is hardly an insight. Additionally, he makes no claim that the Nazis succeeded because of their irrationality; indeed, if they hadn't been quite so adamant about killing all the Jews and taking back the Caucuses, they likely would have been a whole lot more successful.

In short, he has no clear definition of rationality, nor an explanation of how having less of it was good, or having more of it was bad. In the absence of a consistent definition or an explicit claim about methods and results, it seems entirely appropriate for me to use the conventional (around here) definition of rationality as systematically making good decisions that advance your goals.

Now, if his whole argument were, "You can accomplish a lot without being consistently rational," I wouldn't dispute that. But his point is, "You can accomplish a lot without being consistently rational, therefore, rationality isn't all it's cracked up to be." Given that the Nazis probably could have accomplished more if they'd had slightly fewer crazy ideas, he does not appear to support his own claim.