I sympathize with the idea in principle, but do you really think people who are that rich will not find ways to evade the tax? Most likely they can prevent such a tax being installed at all. Money = power.
You are right of course. What I'm opposed to is when poor people (by which I mean everybody except billionaires) claim that there are no other solutions instead of saying that there are plenty of other potential solutions but billionaires won't let us have them.