Why can’t I play that video? All I get is a black rectangle on a white screen, even after I logged in.
That’s very strange. More than likely the video is just not buffering for you, since the first part of the video is just a blank black screen, then it takes you to a warning, then the video itself.
Try closing and reopening your browser.
If it still doesn’t work, go to youtube and just search for “Car Plows Through a crowd of protesters in Charlottesville” by someone with the first name Ahmet, or something arabic.