Miley Cyrus, just like any other girl in the world, has the right to express any feelings or thoughts in any way she wants, even if other people find it provocative or innapropriate. It's okay to disapprove, but you shouldn't harass or shame her for her expression - it's not your place!
Look, Sinead O'Connor is right, and she knows what it's like to be the big thing everyone's talking about. Except, Sinead stood up for herself, didn't degrade herself or demean herself. The fact is, we've all been saying the exact same things. Maybe even less politely. The difference is that Sinead is someone people know, whose stance on women has been supportive. So, listen to her. Please.