Here is the first post on this passage. There are several good arguments there for the understanding of the passage as supporting the traditional visible/invisible church distinction. I wish to add some more, extremely weighty arguments. I owe these arguments to discussions with Wes White.
First of all, if John is saying that these folk who went out “from us” are false teachers commissioned by the apostles, then his rejoinder makes no sense. Why would “they would have remained with us” be an acceptable rebuttal for why they are false teachers commissioned to be sent out? This makes no sense at all. Commissioned folk, according to this intepretation, are by definition sent out. Clearly here, the “not of us” is being here contrasted with “remain with us.” Therefore, it seems highly unlikely that the “remaining” would mean some sort of thing as “remaining in spirit or doctrine,” which would have to be the case, if Wilkins’s view was correct.
Secondly, the purpose clause (ἵνα plus subjunctive) also makes no sense. Why would the apostles send out false teachers in order for them to be exposed? If I were an apostle, and I knew that so-and-so was a false teacher, the last thing I would do is to let him out among the sheep! This would be for a shepherd to let in a wolf in sheep’s clothing in among the sheep! Unthinkable! No, the burden of the passage is that God allowed them to go forth out from the congregation in order that their true origin would be exposed. It is not a commissioning, but a self-induced excommunication that is here related. The going forth was voluntary (the voice of ἐξῆλθαν is active, after all; there were plenty of ways that John could have said “We sent them,” if he had wanted to do so. Plus, the normal word for sending out is apostello).
Thirdly, the definition of “antichrist” in the context is someone who denies the Father and the Son. Their activity is not firstly that of teaching, but that of confessing (vs. 23). They are confessing a denial of the Son, which entails a denial of the Father also. Now, I do not deny that they are trying to teach false doctrine, since that is plainly indicated in verses 26-27. All wolves want to make their own job of eating the sheep easier by trying to convince the sheep that either 1. The wolves are really sheep, or 2. The sheep are really wolves. But this is a far cry from saying that, because these false teachers were commissioned by the apostles, that therefore it cannot be referring to the visible/invisible church distinction. Even if we granted the point about being commissioned by the apostles, that would still not negate the truth of the assertion that they were part of the visible church, but were shown not to be part of he invisible church.