>A lot of people like a carbon tax because it will lower carbon emissions, if you tax productivity it has the same effect.

It's not the same situation, so there's no reason to think it'd have the same effect.

A carbon tax's effect would come from opportunity cost. A company stops a behavior because of a carbon tax when they've found something more profitable. The tax just shifts the line of "more profitable."

But what's somebody going to do if you tax their wealth more? They only "other opportunities" are leaving the country or having more free time. The first is definitely a risk to consider, but the second seems unlikely for the class whose income comes from just investing their wealth. Why not invest, even if the profits are smaller?