He's actually talking about the 9-11 truthers, who are so called because they reject the truth about 9-11, in favour of a set of truly bizarre and stupid ideas - perhaps the stupidest of which is the idea that they are in pursuit of anything that in any way resembles the truth.
Correct. There are so many conspiracy theories out there that sometimes it's tough to keep track of the appropriate terminology.
I think I get it now. If so, your terminology is still fine. I just wasn't sure if was like the holocost deniers, which I'm speculating actually denied that it happened.
In this case, and in line with what Bilby and you say, I'm thinking a 9-11 denier then is a person who denies something related to the event. Not that it happened but maybe why it happened or denies who was behind it, or denies some obvious truth in place of conspiratorial beliefs.
Given your original post, I'm assuming there are 9-11 truthers (as Bilby says) that have some weird belief they hold as true and are 9-11 deniers (as you put it) in that at least some of them deny the possibility that "fire can weaken steel and lead to a building collapse."
You do know that materials used in the building in your link was supplied by the same set of covert operatives that infiltrated the twin towers during construction, right? [/late night humor, lol]