Earlier quoted context omitted.
> The first is that capital gains taxes tend to be on investments made with income you've earned, so there's already been an income tax. I don't really get this counterpoint; isn't everything in the economy a flow of money that has been taxed at a previous point in the flow? If I have $100,000 that I've already paid taxes on, I could invest it in external assets and hope to make capital gains on them; or I could plow…
I am not a tax lawyer, but my understanding is that capital gains only count as such if you've held the asset for at least a few years. By the way, in the first case, your outlays are tax-deductible. (edit: I'm not an expert, so downvoters, please explain your disagreement.)
But in the second case, you're taxed at a lower rate, so the tax code appears to want to discourage you from investing your capital in your own work. If you ever find yourself in a situation where you could make a 10% return on capital by putting that capital to work yourself, or could make the same 10% by putting that capital into a passive investment, the tax code promotes the 2nd option.