Imagine you threw a party. At that party, you had a new-release movie. As you played the movie, you engaged in commentary to your friends. Seems reasonable enough.
Now, imagine instead that you did the same thing, except you did it in a stadium that held twenty million people and you charged all of them.
Twenty million people watching the whole movie the week it comes out in theaters.
Beyond how irritated that would make the creators because twenty million people's first view of the film they've worked years on is overlaid with some jackass cracking jokes, they stand to lose business to you, because now twenty-million people know the entire story, including that amazing twist you managed to keep secret all through production.
A ton of this ill will would go away if creators were getting a per play license fee for the use of their content. Right now, everyone EXCEPT the creators of the original content are getting paid. If people could agree on some standard rates, it would be child's play to have Google simply deduct those from youtube revenue, allowing all parties to get paid in a more reasonable fashion.
Copyright is definitely broken, but if we're looking at who gets hosed in the youtube business, it's far more often original creators than it is youtubers or Youtube itself.