As long as there is a wide ideological division between groups in society, biases and desires can be tapped and manipulated. This allows those in power to direct vast portions of the public down one path or another. When fear of an enemy and the drive to "win" become more important than truth and evidence, the population has tied its own puppet strings and handed them over to the spin doctors.
This is why the false Left/Right paradigm has been so useful to the establishment for so long. Anytime the public starts to wake up to the web of control, all the elites have to do is push one or both sides of the political spectrum towards extremism and let the people rage at each other instead of picking up their torches and pitchforks and tearing down the oligarchy. This method of division and diversion keeps the masses occupied and feeling as though they are accomplishing something while actually accomplishing nothing.