Now, I don't know much about how Warner "ordered" youtube to pull the videos, but whatever the case, I'm not sure they have the authority to do so. One of youtube's legal defenses to having copyrighted materials on youtube is that they don't know who posts videos. Indeed, it could be the copyright holder. If any of Warner's artists have a contract where they have any distribution rights over their videos, they have a right to post their own videos, and warner cannot pull them off. Indeed, depending on what authority Warner is using, this could potentially be a DMCA violation and against the law for Warner to make such a demand. Now, that's speculation on my part, but it is almost certainly true that Warner cannot make a blanket order to remove all videos of their artists.