>it says that we may need to physically fight those whose 'opinions' are backed by force or the credible threat of it.
"Internet radicals" have come to life in the real world, and organized such that they threaten violence, either racist ("race war now") or anti-semitic. Popper's point specifically talks about "rational argument", of which the pure rhetoric (as pointed out by Sartre) is the only tool anti-semites have at their disposal. They do not argue with rational argument.
If my mileage does vary, what then?
Marcuse wrote about the requirement of "rational argument" in 1965:
"Now in recalling John Stuart Mill's passage, I drew attention to the premise hidden in this assumption: free and equal discussion can fulfill the function attributed to it only if it is rational expression and development of independent thinking, free from indoctrination, manipulation, extraneous authority. The notion of pluralism and countervailing powers is no substitute for this requirement. One might in theory construct a state in which a multitude of different pressures, interests, and authorities balance each other out and result in a truly general and rational interest. However, such a construction badly fits a society in which powers are and remain unequal and even increase their unequal weight when they run their own course. It fits even worse when the variety of pressures unifies and coagulates into an overwhelming whole, integrating the particular countervailing powers by virtue of an increasing standard of living and an increasing concentration of power."
I've been trying to avoid an object-level discussion here, because that gets boring pretty quickly.
But the criterion you're proposing applies just as well to Antifa as it does to the Three Percenters, unless you add in a heaping helping of "has opinions I don't like".
Which I'm unwilling to do, because there are people who don't like my opinions, and this kind of thinking gives them ground to persecute me when it's my turn.
So where do I draw the line? Somewhere between the Patriot Prayer crowd and Atomwaffen, basically. The Proud Boys are skirting right along that line, and catching lengthy prison sentences for their trouble. So I think the system we have is working, and don't feel a need to give it more teeth.
I think the kids who show up in black and start street fights are a gift to the far right. I wish they'd hang it up; their hearts are mostly in the right place, but it's strategically stupid.
"Internet radicals" have come to life in the real world, and organized such that they threaten violence, either racist ("race war now") or anti-semitic. Popper's point specifically talks about "rational argument", of which the pure rhetoric (as pointed out by Sartre) is the only tool anti-semites have at their disposal. They do not argue with rational argument.
If my mileage does vary, what then?
Marcuse wrote about the requirement of "rational argument" in 1965:
"Now in recalling John Stuart Mill's passage, I drew attention to the premise hidden in this assumption: free and equal discussion can fulfill the function attributed to it only if it is rational expression and development of independent thinking, free from indoctrination, manipulation, extraneous authority. The notion of pluralism and countervailing powers is no substitute for this requirement. One might in theory construct a state in which a multitude of different pressures, interests, and authorities balance each other out and result in a truly general and rational interest. However, such a construction badly fits a society in which powers are and remain unequal and even increase their unequal weight when they run their own course. It fits even worse when the variety of pressures unifies and coagulates into an overwhelming whole, integrating the particular countervailing powers by virtue of an increasing standard of living and an increasing concentration of power."