Why can’t YouTube automatically catch re-uploads of disturbing footage?

After a man used Facebook to live stream his attack on two New Zealand mosques last night, the video quickly spread to YouTube. Moderators fought back, trying to take the horrific footage down, but new uploads of the video kept appearing. It led many observers to wonder: since YouTube has a tool for automatically identifying copyrighted content, why can’t it automatically identify this video and wipe it out?
Exact re-uploads of the video will be banned by YouTube, but videos that contain