What a silly "analysis."
You could look to Italy, Israel, Austria, the Netherlands etc for examples of the Far right not only flourishing but running government in PR systems without a majority of the votes.
The more you read about those or the AFD the more you'll see how much of their rise has in large part been because of ineffective/unwieldy coalitions. (It's worth reading about the contortions Germany is trying just to keep the AFD out of government.
The notion that it is somehow inevitable that the Far Right will infect every mainstream party in a fptp system is ridiculous. (And why wouldn't it happen with the Far Left, which presumably we would cheer?)
Hell, you know why thr Far Right isn't running France? Right, because Fptp enabled the Left, Centre and moderate Right to stop them.
I get the appeal but goddamn, the more you read about how PR is actually playing out, the scarier it gets. Cherrypicking an example is the absolute worst way to make a point and a great way to demonstrate you don't know what you are talking about.