Longer quote:

> In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise. 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. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. 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.

OK. So he's clearly including advocating for violence as across the line.

My reading of that is that some such advocacy is "across the line". Which is which, is a purely practical judgment. A youtube rando with no IRL power would not concern Popper no matter what she said, while someone like Hitler leading a party of fascists obviously would even if he spoke mostly in dog whistles. Drawing the line requires judgment, not an attitude of "it is society's right to crush those it deems intolerant and society will always exercise that right especially if it makes a military contractor a bit more profit". As we see ITT, Popper was wrong, because authoritarians will often demand that the state exercise such "rights" to the fullest extent.

I think maybe Libya war cheerleaders like B-HL must not have read that last sentence in the quote too carefully.

(I like that you (re)read and quoted his longer quote :-))