> " …the reason that Dweebles don’t believe in footlianism is,
> aside from the fact that it is based on gwivery and is by nature
> dwiverous, because it does not tzoober, and in fact it fails any
> tzoober spectacularly."
As has already been pointed out, this sentence should be rewritten as something like “The reason that Dweebles don’t believe in footlianism is, aside from the fact that it based on gwivery and is by nature dwiverous, that it does not tzoober and in fact fails any tzoober test spectacularly.” You want to know what the main point of the person who says this sentence is (as opposed to his secondary points). O.K., the problem is that dividing things into main points and secondary points isn’t useful, or even possible, based on this single sentence. A better distinction would be between the assertions and the presuppostions of this sentence.
This distinction is a pretty standard one in linguistics and would be useful for explaining what’s going on here. The assertions of a sentence are the new points that it’s trying to make. The presuppositions of a sentence are the things that are already accepted in the conversation and which are only being mentioned, not asserted.
The assertion of this sentence is that footlianism does not tzoober and fails any tzoober test. The presupposition of this sentence is that footlianism is based on gwivery and is dwiverous. The person who said this sentence is assuming that it’s already been established in the conversation that footlianism is based on gwivery and is dwiverous. If it has not been established that this is true, then he is cheating on conversational rules. You don’t say “aside from the fact that X” unless it’s already been established that X is true. (Well, unless you’re being snide and trying to say, “You fool, are you too stupid to notice that X is true?” I suspect that the person you’re arguing with is being snide. As a general rule, I refuse to argue with snide people. It’s not worth the hassle to figure out what they’re saying.)
The person saying this sentence is asserting that footlianism does not tzoober and fails any tzoober test. In other words, that’s a new point in the conversation. But the distinction between assertions and presuppositions has nothing to do with the main points and the secondary points of an entire conversation. To know what this person’s main and secondary points are, we would have to analyze the entire conversation, not just one sentence.