Changes in the capital gains tax rate must not be conflated with changes in changes in the income tax rate. Whereas an increase in the income tax rate results in changes in behavior, changes in the capital gains rate result in an immediate change in value.
At 15%, equity is effectively 85% owned. An increase to 25% results in an immediate loss of value (12%, or [75%/85%]), because future after-tax yield on the stock has declined. While a change has only a one-time effect on the price of existing shares, it has a dramatic impact on new business creation and equity based business expansion. And, since a 12% decrease in price has a far greater impact on accumulated capital gain, raising the rate destroys the capital gain taxable base.