Eh, the distinctions being that

- With YouTube, unlike with torrenting, you aren't distributing the files.

- You have no reason to believe that YouTube doesn't have an entirely valid license - while you do with torrents. YouTube takes reasonable (though not foolproof) steps to attempt to ensure that. Asserting you can't use YouTube because someone might have uploaded a copyright infringing work would lead to the conclusion that you can't browse the rest of the public internet for the same reason.

- YouTube complies with the DMCA for whatever the safe harbor provisions are worth (under US law).

If it's a grey market, it's a very light-grey market.