I may be incorrect, but I thought you could only be denied coverage for an existing medical if you had a lapse in coverage. IE if you were switching insurance companies, the new company would still cover you condition. (Under the old system of course).
IMO thats about the only issue that that the ACA fixed. Allowing people who had lapses in coverage, and who had a preexisting condition to get insurance. Everything else it jacked up, which is what happens to 90% of things the government takes over.