How is calling a powerful person out on what you feel to be an unfair or uneducated opinion "spineless"? That's called "speaking truth to power". Spineless would be saying "Well, she's a rich famous author. I guess we should just agree with her or at least keep quiet".
As for not backing down, what if your feeling or opinion is based on incorrect information? In a previous thread, I said I wasn't going to listen to Piers Morgan because I don't abide the opinions of people involved in the hacking of a dead girl's phone. Because I thought he was the editor of the paper involved in hacking Milly Dowler's phone. Turns out I was confusing Morgan's paper (The Daily Mail), with the paper involved in the hacking (News of the World). While I still don't like Morgan for other reasons, I backed down from my statement because it was factually incorrect.