I think that continuing to discuss the bad parts, like this, is helpful, albeit only gradually.
The people with this attitude are generally either young, healthy people who have never needed serious medical attention, or people who have always had stable jobs that offer good insurance, and have never seen a hospital bill that didn't have 95% paid by the insurance company first. They've never been injured on the job and then forced to pay a year's salary for the surgery they need to continue working. They've never been prevented from starting a business because their employer's group plan is the only way they can afford their life-saving medication. They've generally only seen the system work. In the rare cases they've seen it fail, it has always been for people they don't know closely, and it always looks like an anomaly.
Showing these people that these problems are real, common, and affecting a huge number of people is a start.
Any ideas how?