This is not the case here at all. Camus, as a lapsed Roman Catholic, presumably understood "this whole Christianity thing", though he did not accept its truth. Certainly he felt he understood it enough to form a belief about the obligations of Christians, which he acknowledged in the quotation, and I am not aware of any other writing in which he averred an insufficient understanding of Christianity. Camus simply went on to say that he believed it was not the place of the non-Christian to recall the existence of such obligations to one who professes to accept them. He obviously believed it was
possible for the non-Christian to do so, which necessarily supposes that he believed it is possible for a non-Christian to form such an understanding, which in turn has obvious negative repercussions for your reasoning here. For another matter, I would point out that, as the SkepticWiki entry (which you helpfully linked but seemingly did not read) notes, the fallacy occurs "where an [
sic] participant argues that a belief is correct because the person making the argument is an authority" - which does not appear to describe the case at hand.
As a side point, I assume, perhaps optimistically, that you are aware that a properly constructed argument from authority (
i.e. of the form
There is good reason to believe that P
is true because A
, a legitimate authority, says it is true) - where certain other conditions also apply - is not fallacious. But that's another matter altogether, since Camus is not relying here on any authority.
It is not obvious why Camus' statement need divert us into the question of who is a proper Christian, although I have the impression that by your logic any use of the term
Christian is insuperably problematic. I daresay you are mistaken, moreover, that if you think anything that potentially prompts one to approach the matter of who is a proper Christian must run afoul of the so-called No True Scotsman fallacy. At any rate, the quotation doesn't.
For a discussion of the application, or more often
mis-application, of the No True Scotsman concept to the context of the "true Christian", and the attendant pitfalls, you might consult
this post or
this one. If that raises any further queries in your mind regarding the fallacy, I'll try to answer them, time permitting.
Before we end the lesson on fallacies, however, I'll point out that dismissing the Camus quotation on the basis that you found
Waiting for Godot idiotic is a good example of one, and this would be the case even if Camus had written the play in question. Perhaps I'll use that in a class sometime.
As for the rest of your post, kindness dictates that the less said about it, the better.