John, before you go off in a huff, let's think about a few things like brothers, huh?
First, you suggest primary separation against apostasy. I'll bite. What does that mean? Does that mean that we dare not go out and witness to the lost? Does that mean that we have to toss apostate attenders from our congregations? Or does it mean something else?
I recall, and you know the Scriptures as well as I do, that Jesus told us specifically that we are not to remove the tares from the wheat and more so, that we ARE to go out among the lost and share the gospel.
Yes, we are to remove a sinning brother or sister from our midst, and that after a course of action that confirms that they are sinning so that there is no doubt among the congregation of that matter, but that happens rarely and in many a church never at all.
So, at the end of the day, I remain confused about where and how you would advocate this separation, so perhaps you will need to bring me up to speed as to how it applies. Right now, I'm seeing it as one person's or one congregation's impression that another is straying from the path dictated by the one, and so separation is applied. That is rather nebulous, however, and leads to all sort of excesses as practiced by various congregations and individuals, from those who test new attenders by their practice with snakes to those who wholesale write off anyone who, for instance, is a Roman Catholic, never considering that God brings salvation and justification not some denomination.