I heard that the historical basis for the ongoing denial of UFO's by most world governments is because Winston Churchill said it would threaten the legitimacy of the church.
Did Winston Churchill really claim that?
The claim that Winston Churchill ordered a UFO coverup because he was worried about the mere knowledge of aliens destroying society comes from documents that were released from the British National Archives in August of last year. However, if you look beyond that sensationalist headlines and read the documents themselves it becomes obvious that the story about Churchill and the UFO is thirdhand hearsay, and anachronistic to boot.
The documents in question are letters that a scientist (his name is redacted) wrote to the defense department, looking for information about a "foo fighter" his mother was told about by her father (DEFE 24/2013/1, pg. 284). In other words, the writer's grandfather. The grandfather was, apparently, a bodyguard to Winston Churchill, and claimed to have been present when Churchill was told about a metallic object that had been photographed following a British bomber. Though no date is given for the conversation there is a reference to "the bunker," so we can assume it was during the Blitz of London.
Here's the most interesting bit from the grandfather's story. (Ibid., page 208.)
Of course the term "unidentified flying object" hadn't been coined at the time, so the use of that term can't be correct. It's also unclear how Churchill, or anyone in Britain, could have been so sure what the capabilities of German aircraft might be, considering that Germany was fielding guided missiles that would have been unimaginable a few years before. The story just doesn't ring true. Remember, this is happening years before Kenneth Arnold and the first "flying saucer" sighting. That the earth was being visited by aliens was not even a fringe belief yet, and I find it hard to believe that Churchill and his advisors would make that leap in the middle of a war with an enemy known for high tech air weapons.
The reason for the alleged coverup is given by the letter writer as follows (Ibid. page 279):
Mr. Churchill is reported to have made a declaration to the effect of the following:
“This event should be immediately classified since it would create mass panic amongst the general public and destroy one’s belief in the Church.”
So at a time when Germany was bombing London on a nightly basis and a large chunk of the population of that great city had to flee underground or face fire and death, Churchill was worried that a photo of alien spacecraft was going to shake people's faith? Really? They didn't have other things to worry about, like bombs or the fates of family members fighting overseas? No sale.
Between the anachronistic elements obviously picked up from much later UFO-related pop culture, the hearsay twice-removed nature of the letter, and the unlikely reasoning attributed to Churchill, I don't see any reason to treat this claim as credible at all.
(Incidentally, the Defense Department's only response was that they had no records of the foo fighter or the conversation. Many ufologists will of course claim that's part of the cover-up.)