When the Fascists massacred thousands in Addis Ababa, the U.S. & British govts. ignored it to avoid offending them

Quoting Ian Campbell’s The Addis Ababa Massacre: Italy’s National Shame, pages 336–8:

On 1 March 1937 the British acting consul‐general in Addis Ababa wrote a detailed 13‐page report confirming that the stories of mayhem and depravity collected by the foreign correspondents and the Ethiopian consul in Djibouti were true:⁸ the Blackshirts enjoying the screams of the woman being burned to death in her home as they plunged her children back into the flames; the [Fascist] officer interrupting a burial to rob the putrefying corpse of a dollar—all came to life, in their shame and squalor.
Clearly feeling that the diplomatic language in his earlier telegrams had not had the desired effect, the envoy let his views be clearly known in language normally alien to British diplomacy: ‘The immediate crisis over, there followed for two and a half days, by ways of reprisals against Ethiopians wherever found and however occupied, an orgy of murder, robbery and arson on the part of the [Fascists] that, if the facts were known abroad in every disgusting detail, should make the name of Italy stink in the nostrils of the civilised world.’⁹
On 10 March Emperor Haile Selassie, in exile in his villa in the west of England, submitted a request for the League of Nations to initiate a commission of inquiry into the massacre. Reminding the Secretary‐General of his previous appeals to the League, he wrote, ‘Have you completely forgotten the solemn pledges which you undertook towards the Ethiopian people, and of which I once more demand the fulfillment? […] Will you forget us for ever? […] The massacre of February 1937 will leave on the [Fascist] aggressors a [stigma of] perpetual shame.’¹⁰
But the Emperor’s appeal fell on stony ground; the League took no action. Nonetheless, there was now pressure on London to go public on the issue, and Sylvia Pankhurst organised a protest petition to the Secretary‐General of the League of Nations drawing attention to the massacre, signed by an impressive array of distinguished figures.
It constituted the trigger for yet another pro‐Ethiopia campaign, which would agitate the British Foreign Office mandarins beyond anything they had previously experienced, and—although she had no idea at the time—would run for well over a decade.¹¹
However, scant attention was paid in London to the British envoy’s dispatches; in fact, the Foreign Office falsely claimed in Parliament to have very little information on the subject of the massacre. Then, as we shall see, posing in its self‐righteousness as an honest broker, and supported by America, the British government orchestrated several years of political machinations and intrigue to prevent Ethiopia from succeeding in its quest to bring the guilty to justice.
Finding himself in a dilemma, the Foreign Secretary, Sir Anthony ~~Blinken~~ Eden, sought a course of action that would allow the government to continue to withhold all documents on the massacre from public view, while at the same time appearing to be honest and transparent.¹²
This approach was well received by Neville Chamberlain, Chancellor of the Exchequer, who would become Prime Minister a few weeks later. Anxious to appease Mussolini and determined to suppress Bond’s report, he declared, in a remarkably terse and historic dismissal of the very purpose of the League of Nations, ‘There can be no useful outcome to official protests.’¹³
Reports by the American envoy, Cornelius Engert, were as unambiguous as Bond’s. Describing the Blackshirts’ behaviour as ‘ominous’, his dispatches should have served as a warning of what Fascism had in store. ‘So far as the Italians individually are concerned, these events certainly brought out the man. The veil of idealistic humbug has been torn aside, and the meaning of the self‐styled Italian mission of civilization had been revealed in all its ruthless materialism and sham.’¹⁴
Yet Engert’s insight into the propensity of Fascism to destroy the established moral order was lost on Washington; the American government joined Britain in sweeping under the carpet the behaviour of the [Fascists] in Ethiopia, in the interests of expediency and appeasement.
The whitewash was facilitated by the departure of Bond and Engert from Ethiopia; both men, who knew the situation in Ethiopia well and had personally witnessed the massacre, were transferred shortly afterwards. Bond’s successor called into question the former’s reports of the massacre, claimed that the New Times and Ethiopia News had exaggerated the nature and extent of the reprisals, and declared that the burning of houses in the city had been confined to the immediate vicinity of the Gennete‐Li’ul Palace.
His contradictions were so blatant that it seems likely that he was doing as instructed by his superiors, who wanted to close the file on the Massacre of Addis Ababa as quickly as possible. The irony is that Mussolini was actually very worried about the potential reaction of the international community—so much so that he imposed a complete news blackout.
As Dr. Shashka wrote, ‘Since I have been abroad I hear sometimes that Europe was sorry not to be able to do anything. If Europe was not able to do anything, I ask, why were the [Fascists] so much afraid of Europe? Why did they watch over the telegraph and the wireless station for the news from Europe? Why were the murderers afraid that Europe should know?’¹⁵
The logical conclusion is that the British government would have been in a position to get Mussolini to moderate his henchmen in Ethiopia, if only it had had the moral courage to do so.

We are fortunate to have documentation of this atrocity at all; London only continued to inhibit investigations after the end of the Fascist occupation. Page 3:

The [Fascists] drew a veil over Addis Ababa at the beginning of the massacre by declaring a city‐wide curfew, closing down public telecommunications between the city and the outside world, and confiscating cameras from non‐Italians.
[…]
After [1941] it would have been possible to compile a reasonably complete account of what occurred in February 1937, but Emperor Haile Selassie’s government had to operate at that time under the auspices of the British government, which regarded Ethiopia as Occupied Enemy Territory, and blocked documentation of [Fascist] war crimes.
Furthermore, by the time the Ethiopian government had managed to prepare the basic documentation required, Britain’s opposition to the investigation of [Fascist] war crimes had hardened as a result of [the Kingdom of] Italy changing sides in the Second World War, thereby becoming a British ally.