Now the Irish singer is taking aim at Simon Cowell, telling Ireland's Late Late Show that the X Factor judge has "murdered music."
"I feel sorry for the murder of music and rock 'n' roll," she says in the interview, "which has happened because of the industry. Because of Simon Cowell, [and others, like TV music judge] Louis Walsh. It all amounts to the murder of music."
She goes on to say, "There's a certain alarm that needs to be rung and I know there are a lot of musicians around the country and around the world that will agree. The power of rock 'n' roll to change things, to move people, is being murdered by all this worship of fame, Pop Idol, X Factor, all this stuff."
"What I'm worried about is it's all about the visual, the pyrotechnics, the tit's out...shake your ass. It's not about the song. That to me is quite sad."
Steering the conversation away from the Miley brouhaha, she uses her own experience with the music industry's star maker machinery to illustrate her point.
"I was asked by my record company to start wearing short skirts and growing my hair, and try to act really sexy and that's why I shaved my hair. I wanted to be judged by my talent, if any, and not by how I looked."
Which, O'Connor says, is what prompted her to write the open letter to Miley this week—expressing concern that the young pop star's overly sexual image will become her demise. Miley responded by blasting the Irish singer-songwriter's mental illness on Twitter.
Things predictably escalated further when O'Connor slammed Cyrus for her acts, calling her an "anti-female" and "f--king stupid."
And of course Miley saw O'Connor's scathing letter, and decided to respond via Twitter (again).
Stay tuned. We can't wait to hear what happens when Simon Cowell jumps into this cage match.