Am I just being an overprotective friend?

My best friend, who is a female, is married to the biggest jerk in the world. He constantly puts her down and tells her what to do. She has told me she would much rather spend time with me. But when she tells me these stories, it makes me pretty angry. And I let her know about it. She tells me not to worry about it and that she will take care of it. It never changes and I am getting to the point to where I want to confront him about it. But I am afraid this will ruin our friendship. What am I to do?
Am I just being an overprotective friend?
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