I'm a pre-med student right now and were single payer to pass my career would be over before it starts. Liberals have to realize that healthcare is somebody's labor and you are never entitled to somebody else's labor (slavery) doctors and nurses are overworked as it is and healthcare is 16% of the economy.
That's ridiculous. Labor is just a form of value, and there are plenty of instances where labor is made an entitlement for citizens. The person above noted public defenders, but there's also firefighters and police, services at US embassies abroad, a lot of the federal bureaucracy, and so on.
The fact is, this is not equivalent to slavery and it is morally abhorrent to claim so. No one is forcing doctors at the barrel of a gun to cure people under such systems; instead, it is a condition of being a doctor in the first place. If you think changing your job description qualifies as slavery, I think you might not be cut out for employment of any kind.