When they have no explanation, they appeal to authority, obfuscate, obviate or insult

I don't think G.K. Chesterton quite had this right. From Doubts About Darwinism, in The Illustrated London News (17 July 1920).

And I will add this point of merely personal experience of humanity: when men have a real explanation they explain it, eagerly and copiously and in common speech, as Huxley freely gave it when he thought he had it. When they have no explanation to offer, they give short dignified replies, disdainful of the ignorance of the multitude.

The first part is true - If the claimant knows what they are talking about, they generally are willing and able to explain in common language the basis for their claim.

It is the second part that seems amiss. When they have no explanation to offer, it seems to me that there are four different responses. In roughly the order of frequency.

Appeal to authority

Obfuscate

Avoid answering

Insult the questioner

Appeal to authority is indeed often brief and dignified.

The other three approaches can be brief but usually are not. Obfuscation is usually done at length with jargon and hand waving. Avoiding answering is a common strategy and the claimant usually wants it to be brief but if the interrogator is competent, they pursue until it is clear that the claimant does not know what they are talking about (See Tucker Carlson vs. Bill Nye for a painful example of dogged pursuit of an uninformed claimant).

Depending on how angry the claimant has become once it is revealed that they do not know what they are talking about, the insulting by the claimant can be more or less extensive.