There are nutjob conspiracy theorists, and there are people who debunk their ridiculous claims. What irritates me is when the debunkers get things wrong themselves.
This is problematic. Debunking wrong claims with wrong counter-claims is counter-productive. It only gives even more material for the nutjobs to use for their whacky theories. Debunkers should check their facts and debunk properly.
A few examples:
A common response to "why aren't there any stars in the photographs taken on the Moon?" is "the stars are too faint to be seen".
While this response is not wrong in context, all by itself it's misleading and great source of ridicule by conspiracy theorists. What the answer is trying to tell is that the stars are too faint to be seen by the camera, with its shutter aperture and exposure time settings. These settings were tuned to photograph the very brightly lit lunar surface, and were way too fast for the stars to be caught on film. Photographing the stars would have required much longer exposure times (which in turn would have overexposed the lunar surface). I really wish debunkers would give the unambiguous answer right away, without using a misleading "short answer" like this first. Such "short answers" are very easy to take out of context and misused.
A common response to the "you can see things in shadows, thus there must be more than one light source" claim is, unfortunately, "but there is more than one light source: The Earth."
This response is as ridiculous as claiming that on a bright day on Earth, if the moon is visible, it noticeably adds to the visibility of shadows.
Naturally this is not the reason why you can see things in shadows. The true reason is that light reflects from other surfaces, most prominently the ground, and lights up things in shadows. While the light reflected from Earth might have a minuscule effect, it's almost completely negligible compared to the largest reflector around: The lunar surface (which probably contributes hundreds of times more to the reflected light than the Earth).
This is very easy to demonstrate on the photos: Shadows on the
ground are pitch-black, while shadows on vertical surfaces (such as the
astronauts) are not, as demonstrated on the photo on the right.
This is because there is almost no surface which would
reflect light to these shadows on the ground, while the lit parts of the
ground reflect light to the vertical surfaces. If the Earth was any significant
light source, also the shadows on the ground would be lit, but they are not.
(This is also one good way to debunk the conspiracy theory claims: They claim that light somehow scatters from air and illuminates things in shadows. However, if this was true then the shadows on the ground would be equally lit as the shadows on the vertical surfaces. However, the shadows on the ground are pitch-black, demonstrating that nothing is reflecting light to them. There are of course a few exceptions, where light reflects from the lit ground to the lunar module, and from there to the shadowed ground.)
Still some people make a minor error with this answer too. They say "light is reflected from the highly-reflective lunar dust".
There is an error in this: The lunar dust is actually not very highly reflective (I think it reflects something like 20% of the light). The mistake is to think that the dust must be highly reflective for this to happen.
However, this is not so. That 20% of reflectivity is more than enough. There are many reasons for this, the most prominent one being that the cameras were set up precisely to photograph that 20% of light reflected from the ground. In other words, from the film exposure time point of view the amount of light reflected from the ground is so large, that it makes this 20% to be almost the full brightness the film is capturing. Thus even a small portion of this reflected light, which further reflects from other surfaces (such as an astronaut standing inside a shadow) will be easily captured on film.
(This exposure time is still not enough to capture stars on film. The sun is really bright, and 20% of really bright is still quite bright, much brighter than the very dim light of stars.)
Another contributing factor is that the lunar surface is a really big reflector, which means that a lot of light is being reflected from all directions. This is more than enough to very visibly lighten up things in shadows (especially given that most things in shadows in those photographs are very reflective themselves, such as the white space suits, so they are very easy to see even with dimmer light).
I really wish debunkers stopped using inaccurate physics and inaccurate numbers. That's only detrimental and counter-productive.