Art should be free? Food should be free, medicin should be free and whatever you do for your living - it certainly should be free.
But the music on Spotify isn't free - Spotify pays (and I pay Spotify) for the music. If the Black Keys don't want me to listen to their music... well, I won't neither on Spotify nor in February live in Zürich nor elsewhere.
While I don't think that art should be free, there is no reason to be so greedy.