Bernie wants to get rid of the entire private healthcare insurance industry because he knows socialized medicine and universal healthcare would be well received by a majority of Americans. However, Hillary's approach of enhancing the ACA is a better strategy vs. Medicare For All in this political atmosphere.
I don't know who is correct and would hope that Bernie is. Unless there is a real change in the make-up of the House and Senate, the kind of changes that Bernie wants to achieve are just not going to happen.
So, I'm somewhat convinced by Hillary and Krugman's argument, but ethically/ideologically I'm for universal health. It's debate well worth having without demonizing one side or the other. At the very least, it is an interesting and substantive debate unlike what is happening on the other side.