So for instance, Poppler's paradox is easily used to justify violent intolerance of anyone who opposes unchecked immigration. Not only are they preaching intolerance, but people with very similar-sounding views are actually violently attacking immigrants so it's easy to justify the claim that those ones might as well.
- refuses to debate or discuss its merits and values
- refuses to meaningfully consider or discuss alternatives
- responds to discussion with aggression
The book which includes his quote was published in 1945, Popper was of Jewish ancestry, and the book was speaking primarily about avoiding totalitarianism. His philosophy should be taken in that context. People are manipulating his quote to try to justify intolerance of anything except their own world view, but it is this exact sort of totalitarianism he was suggesting that may imperil an open and free society. In particular he also defined an open society as one "in which individuals are confronted with personal decisions" as opposed to a "magical or tribal or collectivist society."
Intolerance trends towards a closed society where you believe what you are supposed to believe, or face the consequences. Tolerance trends towards an open society where individuals may not agree, but are free to express themselves and challenge one another on any view or value.
> "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 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"