Comment: Not missing the point. If you invest in a stock or bond, you are providing capital to the economy regardless of whether it is your company or not. This change will encourage consumption. "I may as well buy that new German manufactured porsche, because there is now much less benefit to saving- I have to pay 50% tax on any gain I make anyway".
As to your argument about under-utilized capital in large corporations, such a silly argument! The underlying assumption there is that the business is too stupid to invest. If only they knew how to make money, they would be pouring that cash into new factories! Do you honestly believe that is what is going on?