I'm asking that if the millionaire was taxed at the same rate then what would he do with his money instead of investing it?

Same principle with a lawyer being paid $200 an hour, or an actor on $2000 an hour.

Morally I'd say that the millionaire who is rent seeking should be taxed more than those working, but parity would be a start

You make investing seem like gambling. Seems that the IRS treat gambling as earned income, not unearned income.