They cannot know it’s not true, but they could know that it is true.
They’re nonstop denials are giving it away.
Exactly.
They are DESPERATELY trying to convince people that there is nothing there.
Compare this to some other “crackpot” theory. I believe that Apollo 11 did, in fact, land on the moon. There are some who have the conspiracy theory that it never happened. If there were a thread on the topic, I would probably not bother commenting. If I did comment, I certainly would not spend hours/days/weeks arguing with someone who believed it never happened. Why would I? Let them hold onto their kooky theories.
The reason a person would argue so vehemently and so desperately is because they have some sort of stake in it. IMO, they are either being paid to argue or they argue because they are guilty.