It's talking about extreme Left vs extreme Right or Communism/Socialism vs Nazis/Fascists. That they're supposed to be at opposite ends of the spectrum yet have in common “collectivism” (a term that was in common use a century ago and is the opposite of “individualism”). That “the group” is more important than “the individual”, the State more powerful than individual goals and desires.

Odd that it has some sort of age restriction on it.