I stumbled on this brilliant article on the myth vs. reality of Yoko Ono. It didn't tell me anything factual I didn't already know, but the way the author gathers her narrative together and argues her case is stunningly thought-provoking.
What's missing here, which writer Cara Kulwicki admits freely, is any analysis of Yoko's own music. Kulwicki is a Beatles fan, not a fan of Ono's music (though she is a big fan of her activism and conceptual art), and her thrust here is to confront how misogyny works its insidious, ugly way everywhere, even in the hearts of our beloved old idealistic countercultural icons. The link she offers to another writer's critique of Yoko's own body of work is, alas, dead.
Don't let that stop you from investigating some amazing records, though. Plastic Ono Band and Approximately Infinite Universe are great places to start. The Content Providers did not cover "Kite Song" for nothing, I'll have you know.