Well, it makes sense.

You, and everyone else that is able to read this, is literally sitting in front of a globally connected information box, and with a few key taps you can easily bring up archival records and video footage of the holocaust.

So when managing a community that revolves around experts, you have a fundamental duty to their time, the experts won't have all day to answer questions and it makes sense that they would want to answer the interesting or detailed questions. It's not the position of them to have to refute a stance that is taken against what is basic and widely accepted knowledge in our society, and in opposition to what is really high quality evidence.

Now, I think this is different with theoretical fields, like with economics. Because while economic theories rely on practical data, it is a human-made system and therefore can be contested -- did we build it right? That is a melting pot where rich debate can take place, because there has been so much academic and theoretical debate over the last 100 years and much of it is not widely-known.

For example, I doubt many people here will be aware of Meiksins-Wood's book The Origins of Capitalism -- in which she contests that capitalism was not a naturally occurring system -- that is a rich book with a lot of good and firm arguments, and it is worth a discussion.

Whereas with holocaust denial, what exactly can you retort? The argument against the denial boils down to "We have facts, here they are", and the argument in favour of the denial boils down to a rejection of those facts -- it's not very interesting or unique (After you've seen 2 or 3 holocaust denial arguments, they all tend to boil down to one of those three), and it's certainly not something that is worth experts wasting their time over. Much like "the earth is flat", these are situations where people are willingly taking a decision to disbelieve 50+ years of knowledge, and where there is no other interpretation if you actually understand and observe the evidence.

With things like holocaust denial, flat-earthism, you really have to nip them in the bud. They are essentially toxic ideas and people do not go to them out of nowhere.

I have a friend who started disbelieving in germ theory, but she arrived to that viewpoint from the position of having a medical condition that was untreated, for whatever reason it got better when she started drinking fruit-smoothies and using a water filter, that then led her to reading Natural News, and her prior was: "Well, since the medical establishment couldn't cure my illness, what else are they wrong about?". Now, that would have been perfectly fine if she had discovered someone like Ben Goldacre, who works for the Royal Academy of London, and has a medical degree, and works to point out the faults in modern medical practice. Instead, she found a source of misinformation that is known for misquoting official sources and deriving information out of thin air (I used to argue against people who were invested in NaturalNews when I was a teenager -- one of the sources I was presented with boiled down to self-hosted edited papers scraped from pubmed).

Likewise, I didn't believe in climate change when I was younger, because I was brought up by someone who was otherwise cogent, but in this instance she bought into climate change denial, and that influenced a young, impressionable me.

The thing about it is my friend's (and the much younger me's) arguments are like an McEscher drawing, there is no structure, there is no reasoning present -- while it presents itself as reasonable, if you dig into them you will find no architecture, it is just random facts cobbled together that confirm her prior (That doctors and the common body of knowledge are wrong) and ostensibly (to her) prove you wrong. What debating these ideas with her does is prove her contention that she is right, and that everyone else is wrong -- and worse -- it spreads the idea. It exposes new people to the brain worms and allows it to take hold in them.

The only thing left at this stage is damage control -- I was lucky, I was still young and impressionable when I found rational wiki, and the arguments there convinced me to the opposite, but I had to find that by looking -- debating just convinced me in the opposite direction, and likewise with my friend.

So as someone who previous believed in shit like this, we have to stifle and shut down these debates, because they are beyond debate -- no matter what evidence you throw at these people, it will only confirm their believe that you are the delusional one, and drive them further into the hole, while at the same time exposing other people to their McEscher-esque arguments.