Official blog entry from Youtube here.
TL:DR summary from The Verge:
YouTube is changing its community guidelines to ban videos promoting the superiority of any group as a justification for discrimination against others based on their age, gender, race, caste, religion, sexual orientation, or veteran status, the company said today. The move, which will result in the removal of all videos promoting Nazism and other discriminatory ideologies, is expected to result in the removal of thousands of channels across YouTube
About time - and good to see it's so broad-reaching.
It's no doubt going to be hard to enforce, but bravo - at least it looks like they're going to try.
Edit - I've posted this in Off Topic, it shouldn't be a political issue.