And who will decide what is "Extremist Videos"?
This is a dangerous game YT plays now. Who will decide who is a freedom fighter and who is an extremist? Who is good and who is bad?
YouToube is no unbiased public service with higher moral or principled goals. It has to operate in a complicated world with many competing pressures from powerful entities.
For the moment the "reagan meets the taliban" search still points to the right, non-brain-washing videos (https://www.youtube.com/results?search_query=reagan++meets+t...), so on this front we are safe.
On a more serious note, who ever thought this might be a good idea? Censorship never works in this sort of cases, it never has. All it does is it adds legitimacy to fringe beliefs. I for example still think that if it hadn't been for the martyrdoms and censorship they had to suffer early on the Christians and their sect would have had never gained such a following.