Forty percent of federal income receipts come from the first income percentile. We could try to get more from the first 1/10th or 1/100th percentile, but 'income' becomes a nebulous concept. Did Bill or Sam really ever really have any income?

It depends. If you donate enough of your unrealized capital gains, you can cancel out all of your tax owing on what you do cashout and get your name behind whatever causes you want (as long as it counts as charity or politics).

At least that's how it can work out in Canada.

The donations to charitable foundations route is ripe with loopholes that make it attractive ... the charitable foundation can be one that yourself (and a few others who share a tax lawyer) control, an astonishing low proportion of "donated money" can actually flow to the claimed charitable end, and a remarkable percentage of that money can indirectly benefit the people who donate.

Wow that really incentivises pro-wealthy-folks lobbying!

The point is that most don't. There's easy way to avoid paying this tax, outlined in the article.