You keep more of what you earn by having a national health service.

That's true as a collective, but definitely not true in my case, or in the case of most young professionals. Under Sanders's plan for national healthcare I'd pay almost $7K more in taxes. And it's likely that was an underestimate. I do not spend $7K a year on healthcare.

If everyone has to pay then it is fair.

So everyone should have to pay towards my home insurance too then right, because it'd be completely unfair if I was bankrupted over the heinous crime of having my house near a tree and that tree fell on my house. Why not my car insurance too? It seems kind of unfair that if I commit the heinous crime of parking on the street someone can just vandalize it and I'll have to pay for that. Your version of fair is everyone who doesn't earn gets what they want, my version is everyone keeps what's theirs.