An example of deniers are The Mad Revisionists. They are conspiracy theorists who think the Moon doesn't exist. In other words, they are Moon deniers. How would you say "Moon denier" in Latin?
I would write something like: qui negat lunam esse.
I would avoid lunae negator for a number of reasons:
- negator is not classically attested. Nor was it really needed, when it was just as well possible to say negans or qui negat.
- Admittedly, negator is attested in Tertullian (2nd/3rd century), close enough. But he uses negare in the religious sense, to reject Christ or God, and this does not mean to deny the existence (e.g. Luc 12, 9: qui autem negaverit me coram hominibus, negabitur coram angelis Dei – this does not mean Jesus is an apostasy denier).
And that's really the rub: as far as I can see, you can negare a crimen, or otherwise all kinds of allegation, or you can negare a debt (renege on), or a person, but I posit that you cannot negare a thing, such as the moon. Therefore you cannot say qui lunam negat, and therefore also not simply lunae negator.