YouTube is updating its hate speech policies to prohibit videos with white supremacist and neo-Nazi content, the AP reports. The video streaming company says it has already made it more difficult to find such videos, but it's now removing them outright. YouTube will also prohibit videos that deny certain proven events have taken place, such as the Holocaust or, per Vox, the Sandy Hook Elementary School shooting. The changes, which take effect immediately, come as YouTube, Facebook, Twitter, and other online services face mounting concern that the platforms allow, and in some cases foster, extremism. YouTube, which is owned by Google, says it's removing thousands of channels that violate the new policies. (More YouTube stories.)