If a citizen can't be forced to purchase health insurance, why can't hospitals refuse to treat the noninsured?

The argument that requiring people to carry health insurance is unconstitutional may or may not have merit, but likewise what's constitutional about forcing a for profit hospital to treat the cashless uninsured? Why can a hospital be forced to accept Medicare or Medicaid money? Personally I'm for Universal Health Insurance paid for by both tax increment and the usual premium, co-pay and deductible system. Both Medicare and the VA work for me. Both are affordable and far less prone to screw ups or refusal to pay than any for profit health insurance company. The point here is if people can't be required to buy insurance it follows that hospitals should be off the hook for treating them. Cruel, maybe but if there's a principle involved it should cut both ways. Let's discuss!