Well, not quiet so much as oddly obscure...
In his Behind the Smoke Screen (1934), probably the most influential book written on the theory of a knock-out blow from the air, P. R. C. Groves related the following story of angry civilians attacking an RFC aerodrome after an air raid, because they felt they had not been defended adequately:
On several occasions such attacks from the air were followed by episodes indicative of high nervous tension among sections of the public. One of the worst, to which for obvious reasons no reference was made in the Press at the time, occurred at Hythe where, after the raid on May 25th, 1917, a mob invaded a local aerodrome, stoned the mechanics and attempted to wreck the hangars, because the Royal Air Force [sic] unit had not protected the town. As a matter of fact the unit in question was a training school and did not possess a single machine capable of reaching the raiders.1
Along with deaths caused by panic-stricken crowds rushing for shelter and the nightly trekking of people from cities to countryside when an air raid was anticipated, Groves uses this incident as evidence for the fragility of civilian morale under aerial bombardment, with the implication that such things would happen on a far greater scale in the next war. But did it really happen like that? Groves doesn't give a source, and while he was in the RFC himself, in May 1917 he was a staff officer in the Middle East. He wouldn't have had any direct or official knowledge of a riot at Hythe.2
It's not that the story is inherently unlikely: it actually fits the known context quite well. (Indeed, it's just the sort of thing which might lead a government to start planning to suppress large-scale dissent.) The air raid which led to the riot was the first of the Gotha raids, a daylight attack on the Kentish coast which killed 95 people. Folkestone bore the brunt, but some bombs fell on Hythe and two people were killed there, including the verger of St Leonard's; the vicar and his wife were injured. Local feeling certainly ran high; a town meeting at Folkestone passed a resolution urging that the government 'take such steps as will prevent further attacks of a similar nature and the wholesale murder of women and children of the town'.3 Censorship there was. The raid was reported in the press but the location was not revealed (even though the German press had done so). On the other hand, reports of post-raid riots in London had certainly been reported, but perhaps the difference was that in those cases the violence was directed at German shops and the like, not the military. And the aerodrome was variously known as Hythe, Dymchurch or Pelmarsh; it was home to the RFC's No. 1 School of Aerial Gunnery (or alternatively the Machine Gun School), a training establishment as Groves says.
The problem is finding corroboration. The Hythe riot is discussed in some recent secondary works like Andrew P. Hyde's The First Blitz (2002) and Neil Hanson's First Blitz (2008). The latter, for example, says that
Local people, infuriated that none of the pilots had even tried to get airborne, later hurled abuse and stones at the cowering trainees.4
Hanson gives no source for this (neither does Hyde). He adds nothing to Groves (except for that abuse was hurled at the airmen, but this is obviously implicit in Groves anyway), and since he does list Behind the Smoke Screen in his bibliography it's possible that's where he got it from. The problem is that neither Hanson nor Hyde are among the works I would first turn to for a reliable account of the Gotha raids. (Hyde is a potboiler; Hanson is much better but not very discerning, I find.) And the ones I do trust most -- Raymond Fredette's The Sky on Fire (1966) and Christopher Cole and E. F. Cheesman's The Air Defence of Britain 1914-1918 (1984) -- don't mention the Hythe riot at all. Nor do older reliable accounts, such as Joseph Morris's The German Air Raids on Britain (1925) or the relevant volume of the official history, H. A. Jones's The War in the Air volume 5 (1935). It was discussed a few times in the 1930s by writers such as as Bertrand Russell in Which Way to Peace? (1936) and W. O'D. Pierce in Air War: Its Technical and Social Aspects (1937), but again these add nothing new and given their nature are most likely taken from Groves. A search of Google Books and Google Scholar doesn't turn up anything useful.
With one exception: a near-primary source! Maurice Baring's wartime diary was published in 1920. The entry for contains the following, from the entry for 30 May 1917:
We hear that the people at Hythe have stoned the air mechanics because of the German raid. There is not one machine at Hythe capable of getting within reach of a German machine. They are school machines.5
Baring was a staff officer with the RFC in France; in fact he was Trenchard's aide-de-camp. While a gunnery school back across the Channel fell outside his area of responsibility, he was in a position to know about it. So the Hythe riot probably did happen. It's definitely possible that Groves used Baring as a source here: his diary is listed in the bibliography for Behind the Smoke Screen, and nearly all the details Baring recounts are used by Groves. But there is one detail which Groves adds: that the mob 'attempted to wreck the hangars'. That adds considerably to the violence and the threat to authority. Dramatic (and hence, in a work of non-fiction, illegitimate) license? Or did Groves have another source?
P. R. C. Groves, Behind the Smoke Screen (London: Faber and Faber, 1934), 156. ↩
It's conceivable that he found out about it when he was Director of Flying Operations at the Air Ministry from May 1918, though the riot would have been ancient history by then. ↩
H. A. Jones, The War in the Air: Being the Story of the Part Played in the Great War by the Royal Air Force, volume 5 (Oxford: Clarendon Press, 1935), 22. ↩
Neil Hanson, First Blitz: The Secret German Plan to Raze London to the Ground in 1918 (London: Doubleday, 2008), 65. ↩
Maurice Baring, R.F.C. H.Q. 1914-1918 (London: G. Bell and Sons, 1920), 226. ↩