Correct. Once the initial offering is made, the company issuing the stock has gotten their money. That stock will be bought and sold hundreds of times without a single impact to the issuer. The other area where capital gains comes into play is dividend income (which is near and dear to my heart). I can hold my stocks for as long as I want, but after a year, the dividends I receive are considered long term capital gains and taxed at the appropriate rate (in my case, zero on the first 40K or so, 15% on the next 400K or so and then 20% for the rest). The only thing this proposal changes is that the rate goes to 39 percent on income that exceeds 1 million dollars.
Personally, I've had over a million in capital gains only once, and that was a unique set of circumstances (a large holding called at a price that was way higher than I paid for it).