On Extremist content.
I'm with Voltaire on this one:
"I disapprove of what you say, but I will defend to the death your right to say it."

And btw who could even define Extremist content? The government, SJWs, the fake news media?
What one may see as extremist content someone else sees that as the opposite.
The only solution is to stick with free speech otherwise the censorship spirals out of control.