I think the biggest problem isn’t the tax rate, but the fact that the billionaire class can circumvent the tax system entirely

That’s only possible because they’re allowed to buy influence in the system to make it allow for that. In reality, the other threats (they’ll take their wealth to other countries and leave us poor) are bluffing; most of their wealth isn’t portable. Also in reality, most of the policies they demand (and get) aren’t democratically popular, they’re only viable because they spend so much collective money on propaganda and think tanks to get people thinking the money will trickle down or that without them as ‘job creators’ all will be spoiled or lost.

It’s bullshit, and it only works because we let it work. Apparently we need to move in hundred-year cycles between letting the titans of industry squeeze everyone dry before we remember to assert public power to prevent that