Well, it's groupthink, right? People like to stick with people who have similar opinions and ideas because it makes them feel safe, it makes them feel like they belong. People survived by being in groups, and outsiders are violently pushed away for the survival of the tribe.
When you bring over ideas with a label that is so strong - ANARCHY! - the "group" feels threatened.
That being said, you approach is almost "scientific" in nature. In theory, the scientific method allows for disagreement and the testing of conflicting hypotheses until the one that's most accurate rises to the top. It doesn't always happen - scientists being human, they argue and bicker like the rest of us and ideologies occur just as much as in the rest of society. But in theory that approach is so worthwhile! How can you grow without conflicting input? Even if when arguing, 90% of people will not change their original opinion, but how else can you reinforce your position other than being exposed to it's blind spots?
Thumbs up for your post!