I think they're laughing at people who think it was some secret conspiracy, which obviously you do.
Secret knowledge is always a fascinating concept, i am not entirely sure what people gain from believing outlandish conspiracies but they obviously hold massive appeal.
Personally, i think Bigfoot did it. It just makes sense, the FBI and CIA will be too busy looking for "terrorists" to track Bigfoot's movements. I imagine Bigfoot and his asian counterpart, the Yeti, cooked up a scheme to spread religions that would eventually clash with eachother. So you see, i am saying 911 happened and it was planes and terrorists and not some sort of secret plot, i am just saying the whole thing was put into motion by the true conspirators, Bigfoot and Yeti, ancient creatures that invented Christainity and Judaism and Islam, all to lead to an eventual time when they would want to walk out and about instead of hiding in forests and in mountains etc. etc.
Also, that's explains religion. Why Bigfoot and the Yeti invented religion. It's a false flag operation. They made something so stupid, a man in the sky judging everything you do, like eating pork on the wrong day, something so stupid, that people would think "you believe in that, you might as well believe in bigfoot too!" So you see, they spread a lot of silly ideas, so anyone who talks about Bigfoot would just look like another nutcase talking about invisibile men in the sky!
Also, the Yeti, the asian one, is probably pretty crafty and also quite cheap. He is no doubt, the worse driver of the two.