@RexRed,
I don't know that I could give you opinions as a "good Democrat", but here are my fundamental arguments for a public healthcare system.
1) The current system is completely inefficient. Our current model is that for those without healthcare, their healthcare provider of last resort is the emergency room. That doesn't mean that the hospital won't try to collect a huge fee (much higher than from an office visit or clinic), it just means that if you absolutely can't pay, the hospital will eventually sell the debt to a collection agency and write it off. The result is that we encourage people to postpone health care until the situation is severe enough that it requires the most expensive possible care. The result is sky rocketing costs and poor use of health care resources.
2) There are models of far superior systems available. Like Canada. In any system of millions of people, it is easy to find exceptions and Canada is no different. You can find people who had bad experiences in Canada just like in the US, but on the whole, Canadians are very happy with their system and do not want ours. Nor does Canada have "socialized" medicine. You go to your own doctor who is then paid by the state. Don't like Canada? Try Britian where all the doctors work for the state. Or France. These countries are not having the health care issues we are.
3) It hurts US competitiveness to have companies fund healthcare. Ask GM or Boeing about what the rising cost of healthcare is doing to their bottom lines. This problem just doesn't exist in other countries. That provides a critical incentive for companies to cut healthcare expenses at their employees' expense and puts US companies at a significant disadvantage when they cannot pass those costs to their customers. It also means that in slow economic times that companies can cut benefits without the employees having any recourse. Your only option today is to quit your job.
4) It is ridiculous that the richest country in the world cannot provide even basic preventitive care for its population. Just as the school lunch program was founded on the idea that we shouldn't let our children suffer gross malnutrition, I believe we shouldn't allow our population to suffer without access to the most basic of healthcare.