Why would single-payer involve people losing their current insurance? As far as I know, that was a peculiarity of Canada's system; it's not true of the British NHS, or in France or, as far as I know, the rest of Western Europe. The important thing is to force everyone to buy into the government-provided health care system; allowing people to buy private insurance as well doesn't conflict with that.
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"Why must man's vocation always be to distinguish
himself from animals?" http://blog.voyou.org/ -- Baudrillard