You can flag individual videos for hate speech. Every time a video is
removed, it counts as a strike against that account. On the third
strike, the account is disabled; sometimes sooner, if the content is
particularly nasty.

This is actually the most effective solution. If you were to flag an
account with 500 videos, only three of which break the rules, YouTube
staff would need to spend a lot of time (probably hours) trying to
find the infringing videos; time which would be much better spent
reviewing videos that really do violate terms.