The outrageous idea that the Apollo Moon landings never took place are worth discussing, if only because it is worth knowing how to articulate how we know things actually happened. The reality of historic events is an interesting thing to try to prove. It seems so obvious to us that Napoleon lived and that Rome once dominated Western Civilization, and yet what percentage of people could write out anything resembling a historical time line if they were asked?
A profound difference in awareness of history seems to occur with events which are still within living memory. Many people still hear stories from World War II veterans. All but a few World War One veterans have died and direct living memory of that event is fading fast.When I was a child there were still veterans of the Civil War among us, but now that conflict is solely a matter of impersonal history. The number of decades we will be able to hear from people who remember Lunar voyages are limited, while the span of time in which it will become more of a detatched intellectual debate will encompass the rest of human history. This topic has stimulated a lot of hard feelings but with the loss of our will and ability to return to the Moon discussions of this type are an inevitable result of history passing into legend.

We are now as far removed from Apollo as Apollo was from the Spanish Civil War, placing us about a third of the way from when Apollo happened until the time when this too will also pass from living memory. As the centuries pass the less real it will seem, and as original records and artifacts are destroyed through decay and local catastrophes the ability to verify the reality of the Moon landings will grow increasingly problematical.

After we who remember are gone, the very idea that we were once able to leave Low Earth Orbit might seem fantastic. I suspect part of the skepticism concerning Apollo comes from the enculturated belief that progress is inevitable, that our reach will always be further than in the past. People have a hard time believing we once did things we are no longer capable of. While 40 years ago space exploration was striving toward unlimited frontiers, today we are seemingly eternally confined to low Earth Orbit, looking at our past like an aged Russian Gymnast looking at fading photographs of her moment of glory when she was 14 years old. This is what I see as the terrible truth lurking behind the expressions of doubt in our past accomplishments. Perhaps it hurts so much to know we have lost our ability to visit other worlds, that the frontiers we were enticed with as kids have been canceled, that it is better to claim it was all a fraud.

Some clues that we actually visited the Moon.

The fact that photographs exist which were taken in Lunar orbit is admitted even by the hoaxists, but they are probably considered taken by unmanned vehicles such as the Lunar Orbiter series. This suggests any rolls of film showing people and lunar features among the exposed frames would have to be considered by them to be at least partially faked. Orbital hand held video shows details of lunar features not resolvable from Earth, but present in other spacecraft photo datasets which they acknowledge as real, may be more decisive in proving people have at least held cameras near the Moon. In the case of some Apollo missions some landscape features appear in both orbital and surface photos, albiet in wildly different perspectives. If they believe in the reality of one data set, pointing out features visible in both (such as some Apollo 15 orbital pan camera and surface photos) suggests ever more elaborate methods of creating simulations is required.
Convincingly faking a Moon landings requires the existance of high resolution orbital photography first, from which the distant scenery details of a theroetical lunar surface movie set could be made. Delay of weeks to months would be required before sophisticated faked surface photos and painted backdrops could 'possibly' be created. The photos both from orbit and the surface were available essentially at the same time. Of course, the real time video during the surface EVAs show features such as details of mountains which give less detailed previews of many of the landscape elements of the later film images.

Visual effects technology at that pre digital time was relatively crude and a specialty business hardly likely to be a party to government propaganda uses. Explaining the stereo pairs taken on the Lunar surface requires an impossibly large stage.
This sounds stupid to have to justify but a hundred years from now, or whenever the original mission materials are destroyed in one of civilizations periodic catastrophes, it may be more difficult to make people understand that such things once were real. population knows how to read. The idea that Apollo never took men to the Lunar surface is a persistant epilog to this great undertaking which will only grow in popularity as our ability to travel to the Moon fades from living memory. I am confident that at least an intellectual minority will always contain history buffs as long as a decent percentage of the future population knows how to read.

It is not trivial to be lied to about history. There are people with various agendas trying to rewrite history to suit their interests. China does this in regard to its internal and foriegn policy. Hitler, saying "Who, after all, speaks today of the annihilation of the Armenians?",(5) was encouraged by this opening chapter of 20th century genocide and subsequent denial of responsability by the Turks to move this horrific practice into the industrial age. A few vocal proponents even now try to tell people the mass killing of European Jews by Nazi Germany ( the Holocaust) never took place. There seems to me to be broad similarities in the expressed logic of people who spread the stories that the Holocaust never happened and those who insist Apollo was a hoax. That is not to say all Apollo deniers are Nazis, but wide adoption of the idea that vast conspiracies can hide outrageous 'truths' from the public invites 'disconnection' from history and its lessons.