Do you really think investors will stop increasing their money supply if they have to pay 28% instead on 15%?
Uhm... YES, because that's exactly what happens when cap gains taxes are high.
What you have to do is remember that wealthy people don't NEED to earn income from capital gains. They can put their money in security bonds and invest in monetary funds of foreign countries, and NOT use their money to generate a capital gain. They don't really care because they have wealth already, they don't really need any more. Do you think it would bother Romney to not have made $12 million last year?
The thing it REALLY hurts is investments in venture capital. Rich guy has his money socked away in some security investment, where it earns 2-3% interest, and doesn't 'cost' him a dime, because he continues to roll-over the 2-3% year after year. You can't tax what isn't received as income, as long as rich guy keeps his money in the security, he continues to gain wealth year after year, and he will only pay taxes when he takes the money out. You following me so far, pinhead? Now, what we WANT rich guy to do, what we NEED him to do, is to take his wealth out of these securities and invest it through venture capital investments to open new factories and businesses, which will create jobs and prosperity. We can't MAKE him do this, it's HIS money, he can do whatever he likes with it. So what we do to 'encourage' him, is to reduce capital gains taxes, so that he now has a motivation to do this. He may still choose to not do it, but at least there is the motivation of a low capital gains tax, to encourage it.
Increasing cap gains tax rates on the simple-minded notion that all income should be taxed the same, will cause these rich capital investors to leave their money in securities and not fool with it, because they have no reason to do so. They will pay the same tax rates if they receive the money from their securities as if they took a major financial risk with the money and invested it in venture start-up capital. Securities are secure... he's not going to lose money there, he won't make much, but there is very little risk. Capital investments are FULL of risks, and there is the possibility of losing ALL his money. Why would he take that risk if the tax rates are the same either way?