In the former USSR there was a popular joke:

When two people sit down to conspire, one of them is a KGB agent and the other is a fool.

Behind many conspiracy and denial theories is a common flaw, which I shall attempt to show using the experimental method.

An experiment to prove that humans have landed on the moon.

You will need:
A finger.
At least one eyeball, preferably your own.
At least one brain.
Optional:
An office-type swivel chair.
and / or
A railway train or a road vehicle.

Method:

Experiment 1    Hold a finger vertically in front of you.  Repeatedly close alternate eyes whilst fixating on a distant object.  You will see an apparent exchange of left-right location between your finger and distant objects.  If you only have one working eye, or if you wish to further experiment, hold the finger very steady whilst moving the head from side to side.

Experiment 2  Sit in a clear space in a swivel chair and whirl round.  You will observe that nearer object appear to move faster further ones.  If your legs are extended, you may wish to draw them in and observe a speed increase.  This speed increase is due to a demonstrable relationship between the radius of motion of a mass and its velocity.  To make a satellite orbit faster - just push it down a bit.  There you go - all you need is a swivel chair and you're well onthe way to being a rocket scientist!
Adults: Please note that the performance of this experiment after the consumption of alcohol does not count as a valid experiment, however much fun it might be.
Kids: Please do not do this experiment whilst holding an icecream, a drink or a bowl of goldfish - however much fun it might be.

Experiment 3   Whilst travelling in a train or as passenger in a road vehicle, look out of a side window and watch the landscape.  Nearer objects appear to be rushing past your eyes faster than further objects.
(Caution!  Any attempt to perform this experiment as driver may well cause a substantial and fatal location shift.)

Explanation:

When a scene is viewed from different locations, there is an apparent shift of objects.  The apparent shift increases with distance from the stationary  observer.  It increases with nearness for a moving observer.  When the observer is moving, he or she is seeing a scene from a succession of different locations which the brain interprets as a stream of visual data.  In the static case, the shift is more clearly due to location change, but both observations are due to location change and the rules of geometry.

This apparent shift of location is called a parallax shift. It is widely used as a tool in science, and is something that every astonomer should know about.

The Great Moon Landing Hoax?

The denier argument, in brief.  America never landed men on the moon.  The US was worried about the USSR making progress in rocketry.  They were also 'engaged with' other communist countries.  They wanted to do something so spectacular that the USSR would give up on the 'space race'.  There is 'no way' that the technology of the day could put men on the moon, so the US government paid lots of people from Hollywood to help NASA set up a giant hoax.  This hoax fooled everyone.

The Core of the Denier Argument:

People in the US and other countries conspired together to fool the USSR and China.  The big question is, how many other countries?  Given the fact of parallax shift, the answer can only be:  all of them.  Did you get that?  Every country in the world was a part of the conspiracy.  Huh?

Moon-Talk

When those first men went to the moon, just about everybody with a television set was enthralled to see and hear the live action - myself included.  Oh yeah, say the deniers, it was just a Hollywood movie being bounced from somewhere in america.  Mention parallax and they switch to:  well, like I mean, man, yeah, bounced from the moon.  Huh?

In order to convince the entire world, here's what would be needed:

A film is made for every single part of the voyage to the moon.  It is placed in a capsule and transported to the moon.  During the journey, parts of the movie are played at exactly the right time.  Various experiments, accessible from anywhere on Earth are placed on the moon.  This has to be done with great precision, so we need a highly intelligent robot.

A robot on the moon can never be directed from Earth in real time.  Due to the distance, and the limitations of the speed of light, by the time your signal arrives telling the robot to stop, it has already been 'Humpty-Dumptied' down the cliff by gravity.  The experiments must have been placed by an intelligent agent q.e.d.

More on Parallax and Real Science

Вы говорите что я тупоумн?  That's babelfish's Russian version of  'Are you saying I'm stupid?'  You see, for the USSR to fall for something so obviously bogus requires that every soviet radio engineer and cosmologist of that era must be as unintelligent as a Doctor of Dimology with a dodgy degree.

Newton's laws of motion show that for a given mass and velocity,  a spacecraft travelling between the Earth and the moon must follow a specific path.  If a rocket engine is fired, if a maneuvering engine is fired, if a stage is separated - any of these will alter the path.

Now, in order to fool somebody who knows about parallax, which is anyone with at least one working eye, the hoax requires that the Hollywood movie must be transported in a spacecraft with the exact mass, fuel and engines as the one claimed by the hoax.  That includes all of the modules, including both modules of the lander.  If you don't do that, any observer can detect a parallax discrepancy and expose the hoax.

So, in order to fool the public, and most especially the former USSR, the US made a movie and put it in a space craft identical in mass, fuel, thrust and modularity to the one claimed.  If they didn't do that, if they didn't 'really' send a module to land on the moon and return rocks to Earth - using intelligent robots again - then the USSR and China would have been all over them like a pack of hungry astronomers.

Conclusions:

Given the facts of parallax and its implications, given the fact that we have not even today the ability to build such an intelligent robot as would be required, it follows that, since the experiments are in fact on the moon, and moon rocks have been distributed to academics on a planet-wide basis -

it follows that the denier argument is as follows -

The moon landings were a hoax to fool the USSR and China, and the USSR and China were in on the whole gag.
And that argument, my friends, is worthy of the Buzz Aldrin periorbital haematoma award, 2002.

In general, if you analyse a denier argument based on a hoax theory, you will find that, as here

in order for the hoax to be effective, the target audience of the hoax must be a fellow-conspirator.

Q.E.D.