It's not a secret that youtube is riddled with copyright material. If you watch a youtube video that contains copyright are you now a pirate?
By the technicality of the law, yes. You are using a "an application or network that enables the simultaneous sharing of material between multiple users" (From Section 122A(1)(A)).
On the other-hand, by that same technicality any form of multi-computer network use counts, since networks enable simultaneous sharing of material between multiple users.