Earlier quoted context omitted.
I don't think Popper was so daft as to believe that only Soviets and Nazis are capable of the kind of intolerance that should not be tolerated. I'd daresay that democracies happily carrying out repressions, summary executions, lynchings, concentration camps, institutionalized slavery, etc, etc would meet that bar as well. You don't need to drape a swastika around you to be a fascist, you can get by just as well with…
The point is that he wasn't talking about people saying dumb shit on twitter. He's talking about people using intolerance to justify physical violence against people.
> But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols.
The thing he wants suppressed here is the act of 'denouncing all argument' and of 'forbidding their followers to listen to rational argument' and of 'teaching them to answer arguments by the use of (force)'. Any of these Quips remind you of anything in modern discourse? They should.
Because he's not interested in seeing if their grab for power is actually going to work or not, before suppressing it.
To continue quoting Popper:
> We should claim that any movement preaching intolerance places itself outside the law and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.
And a lot of the shit on Twitter today is ranges from skirting those lines to stepping right over them. He views this behavior on a spectrum of borderline-to-actual criminal.
If what he was preaching was 'wait for fascists to start beating people/doing the Beer Hall Putsch/invading Poland before doing anything about them', it wouldn't be called The Paradox of Tolerance. There's nothing paradoxical about stopping intolerant violent action after it starts. What's paradoxical is that you have to stop intolerant violent action before it starts, by stopping intolerant non-violent action.