When napster was the most popular p2p network for pirated music, there was Metallica who hated napster to death, and there was Limp Bizkit, who were pro-napster. Here are some quotes:

There are a lot of bigger problems in the world than whether Napster succeeds or fails...I don't think there is a malice coming out of Napster. We allowed people to tape our concerts from the beginning, and the record company questioned us about allowing that. But my thinking was that it only makes people want to buy more and increases the devotion of people who are going to listen to us. - Dave Matthews (Dave Matthews Band), Rolling Stone, 7/21/2000

We believe that the Internet and Napster should not be ignored by the music industry as tools to promote awareness for bands and market music. - Fred Durst (Limp Bizkit)

There were many more, but just a glance of it is cited.