Because when you put up something for debate, by definition you are creating different sides. Over time, this leads to increasing diversity of opinions and interests, until a state of absolute and total fragmentation is reached. The Western world has already advanced very far along this line of development. Even in the 1940s, you can read plenty of material describing how British leftist intellectuals were cheering at every defeat Nazi Germany would inflict upon their country, because even though they desperately wanted to see fascism defeated, they wanted the Soviet Union to do that, not their homeland.

Individualist democracies endlessly divide the nation. This makes them the most convenient form of government for plutocrats and tyrants who rely on the weakness of others rather than on their own strength. By playing off different factions against each other, the rule of money remains intact. Properly authoritarian regimes embody the opposite principle, where every disparate element is united in authority, by authority, for the common good.