Extremism is political, but it can't be reduced to a simple difference in viewpoints. Cultural/moral relativism, beyond being a bit of a dead end philosophically, can certainly result in an inaction that opens the doors to political degeneration, anti-social behaviour, and terrorism.

As for other forms of media, we do prevent kids from accessing age-inappropriate stuff, more or less in line with developmental psych research [see: Huesmann, Moise-Titus, Podolski, & Eron (2003)]. YouTube is the odd man out here. The handwringing apologia over the appropriateness of a child entertainer using ethnic slurs would be laughable in any other medium.

Google has famously taken a stance on not being evil. It'd somewhat undermine this goal if it were unable to determine what evil is, and isn't.