If it makes you feel any better, it's essentially impossible to convince a moon landing hoax believer they are wrong.
They effectively shine a light on the limits of each person's ability to justify their beliefs, vs. what beliefs are generally accepted just because nobody challenges them.
I've seen a similar effect in several Christian communities in the U.S. If a Christian is mostly surrounded by other Christians, it's easy to accept lots of beliefs because they're not challenged. But if they end up in an environment where people challenge those beliefs, or if there's a lot at stake for holding wrong beliefs, they tend to scrutinize their beliefs much more carefully. I think, overall, they benefit from pruning down their beliefs to a smaller set of better-justified ones.
So to the extent that flat-earthers help others think more critically, I'm glad they're part of public discourse.
When I first heard that the moon landing was faked, I did stop to ask myself "Wait, could it be true?". When I first heard that 9/11 was an inside job and that the folks on the news were "crisis actors", I did pause and ask myself "wait, could it be true?" When I first heard some of Alex Jones' stuff years ago, I again stopped to wonder if there was perhaps some truth to any of it.
To be clear, I don't believe any of those conspiracies. And Alex Jones' stuff hurts my brain. But I have always been of the opinion that it is good that we have a few "crazies" who are "way out there" in our society to serve as a check on all of us. I agree with you: "to the extent that flat-earthers help others think more critically, I'm glad they're part of public discourse." It always felt to me like having a few of those folks around was a healthy balance, even if we mostly wrote them off. Somehow.... it seems like that balance is way way way off today. I don't want these types to disappear altogether, but I'd like to see us get back to some sort of balance.
X percent of people believe the earth is flat and XX% percent believe that aliens that abduct humans.
Some people have a huge issue with this.
The depth of publicly available information about the Moon landings helps a lot too. Most people have only seen a few minutes of video footage at most, and may conclude that Hollywood could fake that video. But the amount of documentation about even the most minute detail of the Apollo program is staggering. If it were all fake,it would be the greatest most detailed work of science fiction ever created. Seriously, it would put Star Trek/Wars to shame. No fiction has lore with such fractal depth of detail as NASA, not even close. Not even Silmarillion comes close.
Since the early 1950s NASA had completely public video feeds for just about everything they did. News organizations around the world had access to the feeds, as well as the freedom to send their own cameras and recording equipment. Newsrooms all over the world have footage in their archives of the same launches, from different angles. And their own copies of NASA footage too. How do you fake all that?
If I remember correctly, during the Mercury program one of the splashdowns was so off the mark that it took the Navy a few hours to recover the capsule. The major US news orgs didn't want to deal with it so they broadcast old footage of an on-target recovery but got caught because other orgs showed the real thing.