if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility.

All silencing of discussion is an assumption of infallibility.

First, if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility. Secondly, though the silenced opinion be an error, it may, and very commonly does, contain a portion of truth; and since the general or prevailing opinion on any subject is rarely or never the whole truth, it is only by the collision of adverse opinions, that the remainder of the truth has any chance of being supplied. Thirdly, even if the received opinion be not only true, but the whole truth; unless it is suffered to be, and actually is, vigorously and earnestly contested, it will, by most of those who receive it, be held in the manner of a prejudice, with little comprehension or feeling of its rational grounds. And not only this, but, fourthly, the meaning of the doctrine itself will be in danger of being lost, or enfeebled, and deprived of its vital effect on the character and conduct: the dogma becoming a mere formal profession, inefficacious for good, but cumbering the ground, and preventing the growth of any real and heartfelt conviction, from reason or personal experience.

First, if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility. Secondly, though the silenced opinion be an error, it may, and very commonly does, contain a portion of the truth; and since the general or prevailing opinion on any subject is rarely or never the whole truth, it is only by the collision of adverse opinions that the remainder of the truth has any chance of being supplied.

The assumption that we are infallible can we justify the suppression of opinions we think false. Ages are as fallible as individuals, every age having held many opinions which subsequent ages have deemed not only false but absurd.

The refusal of free inquiry derives from an awareness of the fragility of the basis of religious faith; and since certainty is psychologically preferable to truth, the former often being willfully mistaken for the latter, anything that threatens certainty is anathematized with fury.

The peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.

They say great minds think alike. That's also true of tiny minds, and it's especially true of closed ones. I'm always impressed by students who know so much about the world they feel no need to listen to anyone else's opinions, aren't you? Especially when they feel compelled to actively shout them down. That's confidence for you. ... Anyone who's unwilling to hear an opposing opinion has no business attending a university, unless they're planning to graduate with honors in bigotry. And they have no business teaching at one either. There's nothing liberal, intelligent, enlightened, civilized or progressive about shutting somebody up because you don't want other people to hear their opinions. Who are you to decide who should and shouldn't be heard? Who made you emperor? It's not only an incitement to public disorder, it's a form of assault and a violation of the civil rights of everyone around you.

When people reject a truth or an untruth it is not because it is a truth or an untruth that they reject it.
No, if it isn't in accord with their beliefs in the first place they simply say, "Nothing doing," and refuse to inspect it.

the English philosopher John Stuart Mill argued that silencing an opinion is “a peculiar evil.” If the opinion is right, we are robbed of the “opportunity of exchanging error for truth”; and if it’s wrong, we are deprived of a deeper understanding of the truth in “its collision with error.

Only those afraid of the truth seek to silence debate, intimidate those with whom they disagree, or slander their ideological counterparts. Those who know they are right have no reason to stifle debate because they realize that all opposing arguments will ultimately be overcome by fact.

4. The falseness of an opinion is not for us any objection to it: it is here, perhaps, that our new language sounds most strangely. The question is, how far an opinion is life-furthering, life- preserving, species-preserving, perhaps species-rearing, and we are fundamentally inclined to maintain that the falsest opinions (to which the synthetic judgments a priori belong), are the most indispensable to us, that without a recognition of logical fictions, without a comparison of reality with the purely IMAGINED world of the absolute and immutable, without a constant counterfeiting of the world by means of numbers, man could not live — that the renunciation of false opinions would be a renunciation of life, a negation of life. TO RECOGNISE UNTRUTH AS A CONDITION OF LIFE; that is certainly to impugn the traditional ideas of value in a dangerous manner, and a philosophy which ventures to do so, has thereby alone placed itself beyond good and evil.

There is no method of reasoning more common, and yet none more blameable, than, in philosophical disputes, to endeavour the refutation of any hypothesis, by a pretence of its dangerous consequences to religion and morality. When any opinion leads to absurdities, it is certainly false; but it is not certain that an opinion is false, because it is of danger-ous consequence. Such topics, therefore, ought entirely to be forborne; as serving nothing to the discovery of truth, but only to make the person
of an antagonist odious.

But the peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.” — John Stuart Mill1