They're quoting a paper by respected economists, but feel free to discard it because it doesn't fit your priors.
And no, you didn't specifically say effective tax rate, but you did say that western countries effectively had a cap on how much you could earn (presumably that's what you meant, even though we're talking about a wealth tax here, not an income tax, but I digress), given a top marginal rate near 100%, but that's simply false, given that the effective tax rate even for the absolute most wealthy Americans was closer to 50%.
It's a little like complaining that university has gotten so expensive by just looking at the sticker price, while ignoring the fact that few people actually pay that, and the median price actually paid is much lower. That doesn't mean the effective price is where it should be either, but you do your position no favors with falsehoods.
And no, you didn't specifically say effective tax rate, but you did say that western countries effectively had a cap on how much you could earn (presumably that's what you meant, even though we're talking about a wealth tax here, not an income tax, but I digress), given a top marginal rate near 100%, but that's simply false, given that the effective tax rate even for the absolute most wealthy Americans was closer to 50%.
It's a little like complaining that university has gotten so expensive by just looking at the sticker price, while ignoring the fact that few people actually pay that, and the median price actually paid is much lower. That doesn't mean the effective price is where it should be either, but you do your position no favors with falsehoods.