There is no agreement. TOS is a notice not a contract. It's not stealing because it's public content, publicly accessible to anyone with the technology to do so.
If Google wants to make YouTube a service with actually binding contracts and not TOS notices no one reads or respects, it can put the whole thing behind a login and end un-authed public web traffic. They're free to do that but they won't because they know that would kill the site dead, and quickly so.
If Google wants to make YouTube a service with actually binding contracts and not TOS notices no one reads or respects, it can put the whole thing behind a login and end un-authed public web traffic. They're free to do that but they won't because they know that would kill the site dead, and quickly so.