Why is it that all republican plans for health care reform prevent sick people from getting health insurance?

I've read all of their plans. They would create competition, but also destroy all safe havens in health insurance for people with pre-existing conditions as well as remove state laws that protect the consumer from misleading practices.
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That's absurd. Do you realize that only 11% of Americans lack any form of health care? (Check the census bureau website.) Most of those are 18-34. Why institute a sweeping comprehensive government-mismanaged system to cover 11% of the population?
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