The main reason this tax is brought up, it will never be passed, is because it wants to do away with a progressive tax. The reason it wants to do away with a progressive tax is two fold. Number one, in the US Constitution it explicitly says, no progressive taxes. Number two, this reason is mainly a austrian economics thought but anyways, the idea is that the rich are the people who propel the economy forward through their use of capital. Taking the capital and money away from them and giving it to the poor, or even with less sense wars in foreign countries, just lowers the rate of investment in the economy thus slowing it down.