I would probably put $100 more toward principal each month on my mortgage. Does that count as spending or saving or both? Regardless, the point is that if you divvy up the money to millions of low and middle class individuals rather than giving it all to ultra-wealthy individuals, you at least have some chance of having that money spent. Will 100% of the money be spent right away? Probably not. But to a multi-billionaire, there's zero chance he or she would spend any considerable portion of that money. Ever.
If a business owner got an extra $5000, chances are he would expand his business and give one person an extra $50,000. That would contribute to the economy much more than giving everyone $100.
And why would a business man feel compelled to expand his business unless the demand warranted it?
If you raise taxes on the rich, they'll just use accountants to find more loopholes to avoid the tax. Flat tax at a low rate, no loopholes, and the inequality between millionaires and the middle class will disappear.
Whatever loopholes exist already exist, and they're being used regardless. Raising the tax rates doesn't automatically make more loopholes appear.