It's widely accepted that, when you tax a certain behaviour, the frequency of that behaviour decreases.
For instance, my colleagues in the CSN are calling for inequalities to be taxed in order to reduce inequalities. It would make more sense to acknowledge that taxing investment reduces investment, as is the case with all taxes. Consider the tax on tobacco and just about every other tax.
That isn't a matter of theory or some formula on a university chalkboard; unfortunately, it's a fact. We can lament it all we want, but it doesn't change the fact that investment decreases when it is taxed.