I disagree. It is a matter for debate because I do want it, and so do a lot of people.
Do you want to compare the percentage of people killed by the NHS to the number of people who died because they put off going to the doctor or who couldn't afford their medicine? Also, medicare for all doesn't propose to copy NHS. NHS actually owns the hospitals in the UK. The system most often proposed here would simply make the government the single payer for insurance claims. Hospitals would still be free market.
I'm going to be straight with you: you will eventually lose this fight. The cost of medical care goes up yearly and it will continue to go up due to our aging demographics. Our current system is the most expensive in the world and when compared to the other top spenders, we aren't really getting much out of it. None of them leave us in the dust or anything, but they beat us on some key metrics. And on the metrics we beat them on, we don't leave them in the dust.
If the free market can bring it to us better, faster, cheaper, then they should. And if they can't...then this will be one of the examples of things we conclude the profit motive isn't useful for. We don't have for profit police, fireman, or soldiers. Maybe we don't need for profit medical insurance either.
The pendulum of public opinion swings back and forth, and eventually we will have the votes necessary to make it happen. And none of the countries that have gone universal care are clamoring to go back.
So, if you don't want us to go in 100%, it would probably be a good idea to find a compromise. The obvious compromise would be to have a public option.