And once again, the quote in broader context:

"How can one choose to reason falsely? It is because of a longing for impenetrability. The rational man groans as he gropes for the truth; he knows that his reasoning is no more than tentative, that other considerations may supervene to cast doubt on it. He never sees very clearly where he is going; he is "open"; he may even appear to be hesitant. But there are people who are attracted by the durability of a stone. They wish to be massive and impenetrable; they wish not to change. Where, indeed, would change take them? We have here a basic fear of oneself and of truth. What frightens them is not the content of truth, of which they have no conception, but the form itself of truth, that thing of indefinite approximation. It is as if their own existence were in continual suspension.

But they wish to exist all at once and right away. They do not want any acquired opinions; they want them to be innate. Since they are afraid of reasoning, they wish to want the kind of life wherein reasoning and research play only a subordinate role, wherein one seeks only what be has already found, wherein one becomes only what he already was. This is nothing but passion. Only a strong emotional bias can give a lightning‐like certainty; it alone can hold reason in leash; it alone can remain impervious to experience and last for a whole lifetime.

The anti‐Semite has chosen hate because hate is a faith; at the outset he has chosen to devaluate words and reasons. How entirely at ease he feels as a result. How futile and frivolous discussions about the rights of the Jew appear to him. He has placed himself on other ground from the beginning. If out of courtesy he consents for a moment to defend his point of view, he lends himself but does not give himself. He tries simply to project his intuitive certainty onto the plane of discourse. I mentioned awhile back some remarks by anti‐Semites, all of them absurd: "I hate Jews because they make servants insubordinate, because a Jewish furrier robbed me, etc."

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 theyseek 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. It is not that they are afraid of being convinced. They fear only to appear ridiculous or to prejudice by their embarrassment their hope of winning over some third person to their side.

If then, as we have been able to observe, the anti‐Semite is impervious to reason and to experience, it is not because his conviction is strong. Rather his conviction is strong because he has chosen first of all to be impervious. He has chosen also to be terrifying. People are afraid of irritating him. No one knows to what lengths the aberrations of his passion will carry him — but be knows, for this passion is not provoked by something external. He has it well in hand; it is obedient to his will: now he lets goof the reins and now he pulls back on them. He is not afraid of himself, but he sees in the eyes of others a disquieting image‐his own‐and he makes his words and gestures conform to it. Having this external model, he is under no necessity to look for his personality within himself. He has chosen to find his being entirely outside himself, never to look within, to be nothing save the fear he inspires in others."

The issue is that by utilizing partial quotes from Popper and Sartre in order to justify presumptive bad-faith censorship, proponents are literally "loftily indicating by some phrase that the time for argument is past" solely through an argument from authority.

If I said, without citation, that "Our opponents can only argue in bad faith. Our self-righteousness is infallible because we're sincere and they are not. Never challenge their arguments or sincerity directly, because they will use your generosity against you without ever changing their minds." but without citation of a famous name, how would people evaluate this position?

Outside of who said it, I'd wager that most people would say that it presumes bad-faith and can only serve to ratchet-up and escalate any division already present. If any genuine attempt to understand or be understood was present, the proponent has shut it down from the outset.

Now when you attach a name to it, suddenly that same argument, given different verbiage, suddenly garners either knowing nods of self-righteousness or visceral renunciation, despite the content being quite identical.

Compare your selective Sartre quote with the following:

"The more I argued with them, the better I came to know their dialectic. First they counted on the stupidity of their adversary, and then, when there was no other way out, they themselves simply played stupid. If all this didn't help, they pretended not to understand, or, if challenged, they changed the subject in a hurry, quoted platitudes which, if you accepted them, they immediately related to entirely different matters, and then, if again attacked, gave ground and pretended not to know exactly what you were talking about. Whenever you tried to attack one of these apostles, your hand closed on a jelly-like slime which divided up and poured through your fingers, but in the next moment collected again. But if you really struck one of these fellows so telling a blow that, observed by the audience, he couldn't help but agree, and if you believed that this had taken you at least one step forward, your amazement was great the next day. The [category] had not the slightest recollection of the day before, he rattled off his same old nonsense as though nothing at all had happened, and, if indignantly challenged, affected amazement; he couldn't remember a thing, except that he had proved the correctness of his assertions the previous day." -- [famous person]

Ignoring if people recognized the actual provenance, if I put anti-Semite and Sartre, it'd be upvoted, and if I put Jew / Hitler, it'd be flagged within minutes, yet it says exactly the same thing. And leads to exactly the same dehumanizing attitudes towards living, breathing, fallible human beings.