When someone has been shown bogus photos, or only given one explanation for a piece of evidence, they can be mislead into spreading that disinformation. If those people can be shown the errors in reasoning, or the evidence can be shown to be bogus, those folks might, just maybe, be more amenable to a reasoned explanation if they aren't labeled kooks or crackpots right off. For this particular guy to make the effort to seek out Buzz Aldrin with his crap conspiracy, I think he falls on the side of the fence with an agenda, and no, I don't think those people can be reasoned with. They have a reason for spreading their conspiracies that overrides the truth.
You mentioned jryan before. I'm not sure which category he falls in, someone with an agenda or someone who was misinformed and is simply passing on a bad argument, but the second post in his "Is 'Consensus' shifting?" thread used terms like "stupid" and "non sequitur" and I think that made him unnecessarily antagonistic and determined in his future posts. It could well be that he has some kind of agenda that made him turn to fallacies in order to "win" his argument, but it may have just been that he was being stubborn due to being labeled, pigeonholed and marginalized.
Buzz just asked the guy to get away from him while the guy was claiming he didn't walk on the moon. Buzz didn't hit him for his misinformation or his stance. Buzz hit him because the guy got in his face and called him a coward and a liar. If that was 100 years earlier, Buzz could have shot him dead.
It's one thing to question evidence. It's a whole other thing to call an Apollo astronaut a coward to his face.