I'm sorry, I don't understand. What's the problem with what OP's co-worker said. She didn't think the protests were effective or useful. Surely she's entitled to feel that way?

Edit: the gist of your post seems to be that expressing political opinions at work is only acceptable if you agree with them. That's obviously nonsense. Either everybody can do politics at work, and you have to accept that some people will disagree with you, or nobody can do politics at work.