If a person can't afford health insurance, they probably can't afford to get sick. If that person winds up in the emergency room and can't afford to pay the hospital, the cost of his or her care will get passed along to those who are insured. The hospital has to mitigate that loss, so hospital rates go up, and insurance companies raise premiums. If the hospital is city owned or if the person qualifies for Medicaid, tax-payers are paying for that health care. That's not the whole story on price increases, of course, but it is the story on whether an insured person "should have to" pay for health care to uninsured.
These people who can't afford health insurance aren't necessarily unemployed or working in this country without documentation. My husband was self-employed, so he didn't have employer insurance. My son works for a small business, and the best deal they could broker with so few employees cost him $200/week to insure his family. I work for a small university, and insuring a family costs $600/month. The cost would be less at a large university. And people who work for large cities, the state, and such big employers will benefit from the deals their employers can broker with the insurers.
So the category of uninsured is likely to include many people you do business with. Small business are hurt by the current situation. People who are insured are ALREADY paying for health care for people who aren't insured, including unemployed citizens and undocumented workers.
The uninsured also includes insured people with a chronic disease who lose their jobs and, when rehired, are refused insurance because (a) they had a break in coverage and (b) they have a preexisting condition. Preexisting conditions can include pregnancy. This is what happened to the woman who had lupus, lost her job, was unable to get insurance because of preexisting condition, and died of a treatable disease. She finally was so sick that she visited the ER, was admitted to intensive care--and after hundreds of thousands of dollars spent on her care--the died. With proper health care, lupus doesn't have to be fatal. And the costs for her care were passed along to tax-payers and the insured. It would not only be morally just, but also thrifty to provide health care to keep people healthy
A person who can't afford to see a doctor or pay for a prescription may spread disease, e.g. strep throat, to other people. So it's also a public health issue.
This is why I find the firefighter comparison so useful. When fire companies were private, a person had to subscribe to obtain fire-fighting service. If my neighbor didn't subscribe, her house would burn down. If I subscribed, the fire company might be on hand to see to it that her fire didn't spread to my house. But in any case, her problem was very likely to become my problem.
When fire companies were taken over by the government, everyone got better care. Yes, it may have cost me more than my subscription to the private company, but now my neighbor's fire is less likely to spread to my house. We pay for fire-fighters through our taxes and we get good value for our money, even if we never require their services.
I remember when the state made auto insurance mandatory. There was a horrible outcry about big government. But now I expect people are glad that insurance is required. But how does the government make people buy auto insurance? Well there's the citation, but that's not really going to help if an uninsured person causes damage to your car or your person. So we pay an "uninsured motorist" insurance cost, even though insurance is required. And insurance companies created pools where people could get insurance more cheaply, if they meet the criteria.
That's the point of the public option with the health care reform bills. If we require people to have health insurance, some people will not be able to afford it. So we have to have a way to make it affordable to them.
The second reason to have a public option is that it will increase competition, which will encourage insurers to reduce rates.
The high costs of the uninsured are borne by the tax-payers and the insured. Reform is essential and the public option is both morally justified and financially justified.