Of course they should. Even Nixon charged a marginal tax rate of above 70%. Roosevelt charged 94%. It is not only a matter of fairness, but not doing so is also very dangerous. Billionaires shouldn't exist. A few had a ton of merit. Many inherited. All of them were very lucky, regardless of their merit and effort. But none of the billionaires was elected by the people to have the completely disproportionate power they have over society.

So, while I am completely for capitalism and low taxes for everyone, including the wealthy, billionaires should be taxed out of existence. Basically, I think the tax rate curve should be like a hockey stick. Very flat and then suddenly all the way up to almost 100%. The old billionaires would still be able to live very comfortable lifes as millionaires.

No single country should be doing this by itself, though. It should be a coordinated effort.