Automation is the only real solution. These types of conversations seem to always overlook how normal people don't want to watch such videos. Do you want to spend your day watching this stuff to grade them?
Could those not apply here?
What about providing more tools for community to categorize disturbing videos other than simply "flag".
That makes me not normal, I guess. Plus, the NSFL videos were almost instantly taken off YT immediately after having been uploaded, what had remained was really interesting stuff documenting the war in Syria (or at least interesting for people such as myself, a guy interested in wars and conflicts in general).
I'm pretty sure there's a healthy chunk of population who would be unfazed and would love a cushy job judging videos.