People should be allowed to ask questions. It's only when they do that we get good answers. In the absence of dispute, everything, even a fact, is reduced to dogma.

These days J.S. Mill is often framed (by those arguing against free speech) as saying that "free speech leads to truth". But Mill was no fool and that was not his argument. From https://en.wikipedia.org/wiki/On_Liberty:

> 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.

Mill says that, without disputation, we cannot get to truth. This is not the same as saying that disputation will always lead to truth. Mill also makes an important distinction (that we no longer recognize) between correct opinion and correct opinion that is rationally grounded.