So you're agreeing that a business person will invest if they see opportunity to make money.
A 25% tax rate is not going to stop any significant amount of investment. The uncertainty of what the rates are going to be are a far bigger roadblock to investment than the actual rates themselves.
Yes, they will invest when they see an opportunity. They're also only likely to invest if they feel their investment will return X%, either because they will wait for another opportunity or, simply, feel the investment may not be worth their time.
An increase of tax rates will have a material effect on their real-cash ROI and in instances with push investments from above X to below X, and thus decrease investment.
I'm not saying I don't think capital gains rates should be raised. I think it's something worth looking into but the basis of your argument is flawed.