These are all very good reasons, but in practice it mainly means that the richer you are, the less you pay in taxes as proportion of your overall income, and there's a point past which taxation is essentially regressive as a result. So any such argument has to demonstrate that the obvious disparity that already exists in that arrangement is less of a problem than any of the hypothetical problems from taxing capital gains more.
Especially since there are countries that do tax at least some capital gains at the same rate, and they don't seem to be doing appreciably worse than other countries in a similar economic bucket that do not. Indeed, it seems to be more popular among economically liberal countries with flat income taxes.
> Every level of income pays a higher rate of taxes than the level below it according to IRS reports
Does their definition of "income" include capital gains for the purpose of those reports? I don't see how this could possibly be true if it does, given that capital gains constitute the largest part of overall income past a certain point on the scale.
I'm not sure where it is today, exactly. But it's easy to see that it's always going to be there, simply by virtue of increasing proportion of capital gains at higher income levels.
Especially since there are countries that do tax at least some capital gains at the same rate, and they don't seem to be doing appreciably worse than other countries in a similar economic bucket that do not. Indeed, it seems to be more popular among economically liberal countries with flat income taxes.