>But the AI would not be able to perform live on a stage

The vast majority of music consumption is by people that have never seen the artist live. Hell, I have no idea myself if there is a human behind it.

>what gives the right and permission for humans to exist anymore?

Nothing. We are just a mote in incomprehensibly small fraction of eternity. Eventually the process of equalizing entropy will erase all traces of our existence. Enjoy it while you have it.