Because money is power. If you believe in democracy, then extreme inequality is extremely un-democratic. (Note, there is, IMHO, a happy middle-ground: some amount of tolerable inequality, resulting in some amount of tolerable un-democratic-ness)
Money isn't power. Power is power. Money can sometimes be used like power, but not knowing the difference is a recipe for the situation we find ourselves in now.
Money is only powerful as long as it's useful. When the pitchforks come out, dollar bills won't stop them.
