> it's not about adding income tax rate to someone that already pay income taxes, it's about making wealthy people, who don't currently pay this tax rate, pay the same rate as people living from their income.

That's exactly it. I've been really shocked at the willful ignorance (or deceit) coming from the billionaire class on this. I mean, OBVIOUSLY the practical operation of the tax regime is unfair at the top end. If you put a billion dollars in assets somewhere, almost any asset (including e.g. stock in a company you can't sell because you need to own it), growth of that asset is (1) trivially liquid via loans[1] or deals and (2) COMPLETELY UNTAXABLE IN PRACTICE because there's never (ever!) going to be a point where it's traded or converted in such a way that it becomes a "capital gain".

[1] e.g. Bezos goes to Citi or whoever and writes up a contract for a $100M loan to be collateralized with ever-appreciating AMZN shares, likely at a deeply discounted rate (low risk, plus the "keep Jeff in the rolodex" benefit to the bank) then pays it back on schedule with another loan taken out on his now-even-larger stake in AMZN. Who pays the tax here? It's not "income"!