It's not that universal healthcare = no fascism. People in France are being squeezed the same as people in the US. Yes, they are starting from a better place having universal healthcare, but decline is decline and feels bad even with healthcare. People are going to look for someone to blame.
It's true, the claim more left-wing economic policy will weaken far-right popularity has been proven wrong. But the claim that adopting some of the far-right's social policy will weaken far-right popularity has also been proven wrong. Other people being wrong doesn't automatically make you right.