It's dangerous because of its rhetorical style. The way it's written is almost hypnotic. It relies on oversimplifications and excessive uses of repeated phrases that almost become a chorus within the text to the point where it clearly has the potential to negatively affect people who read it if they're a little bit suggestible or if they're not prepared to deal with what they're reading critically. While obviously not solely responsible for this phenomenon, I feel like in my experience, someone reading Nundere and believing it is an act that prepares them to uncritically receive other anti-government information as fact.