After all, it's not like millionaires will stop working if we take 70% of their income in taxes, is it? It's not like millionaires who want to keep working will move out of state if we take 70% of their income in taxes. It's not like millionaires who don't want to move will hire an accountant to hide their income if we take 70% of their reported income in taxes. What could possibly go wrong if we levy punitive taxes on the most productive citizens in the state?
Actually, what millionaires will do, if they live in Minnesota, is move. Or at least move their assets elsewhere. The net effect of confiscatory taxes is that people will go to great lengths to minimize those taxes.