The Sartre quote on Anti-semites, where is it when you need it? Oh hey, wait a second.
“Never believe that anti-Semites are completely unaware of the absurdity of their replies. They know that their remarks are frivolous, open to challenge. But they are amusing themselves, for it is their adversary who is obliged to use words responsibly, since he believes in words. The anti-Semites have the right to play. They even like to play with discourse for, by giving ridiculous reasons, they discredit the seriousness of their interlocutors. They delight in acting in bad faith, since they seek not to persuade by sound argument but to intimidate and disconcert. If you press them too closely, they will abruptly fall silent, loftily indicating by some phrase that the time for argument is past.”
I'm not a fan of the 'punching nazis' wing here, and I think the people who think too much about 'punching nazis' have their own issues. But engaging every extremist in argument, and by opposing, end them? Lofty, but impossible.
The problem is you have people who are both A) arguing in bad faith, and B) causing harm (even if that harm is as trivial as derailing the conversation and starting hostilities). Engagement achieves nothing, since by arguing in bad faith they attack the debate itself: you are trying to 'engage' with someone who will not actually engage with you except on a superficial level necessary to cause you consternation/frustration and in doing so discredit your argument. No debate is actually happening (or indeed, possible), but the fiction of the debate allows them to challenge the credentials of their would-be opponent, even though they would not actually participate in a real debate should their opponent accept. So finally I think it's sort of ridiculous to have this position that if we aren't engaging them in debate when they don't want to be, that frustration, and even blanket rejection, isn't a fair position.
I understand that convincing people to abandon their terrible views is important, and it absolutely can be done, but many extremists are not willing to be honest about their arguments, and so there is a need to engage with something they
aren't saying (will still trying to be
understanding and not dismissive).