You're focusing on the trees. Who do you think pays the private health care premiums for your hypothetical startup? The insurance fairy?
That money comes out of your pocket, today -- not out of (speculative) future capital gains dollars. And since it's nearly always more expensive (per head) to insure smaller groups, you're very likely going to pay more by insuring your own small company, versus participating in a national program.
That said, I don't necessarily think that capital gains are the best place to find money for health care. But if it came down to a choice between raising capital gains taxes (which are quite low in this country) to fund universal coverage, and eliminating our already meager capital gains taxes to "promote" small business, I'd take the health care in a minute. And I'd still start a company, because my expected upside will massively exceed any loss due to taxes -- again, it's all about perspective.
At the end of the day, the "taxes discourage business" canard only works for the ultra-rich, who already have significant capital gains to protect. For the rest of us, it's a much better deal to get guaranteed health coverage.
Canada: 8 weeks for heart surgery
America: Next Week.
Nova Scotia: 25 weeks for a specialty consult
Iowa: 1 week for a specialty consult
http://www.cbc.ca/health/story/2007/10/15/waittimes-fraser.h...
People don't avoid starting companies because they're afraid of the capital gains tax on their anticipated profits (At least, people with a healthy dose of perspective don't do this).
If you're going to pick from the list of reasons that people avoid starting companies, at the top of the list has to be the fact that most are afraid that they'll be unable to take care of themselves and their family during the lean times. Universal health coverage is an obvious step toward alleviating this fear. The abstract, vague notion of someday paying a (rather low) tax on the eventual, theoretical profits from the venture doesn't even come close.