Putting your two statements together, we are to separate from MacArthur because he has been disobedient in failing to separate from Hayford.
You simultaneously identify something as the same and not the same.
Maybe I am dense (insert your own punchline here) ... but I am not sure what you are saying. I am not following you here.
What I am saying is this: Romans 16::17-18 commands believers to separate from false teachers. When MacArthur fails to expose and separate from Hayford, he is violating that biblical command.
2 Thess 3:6-15 tells us how to respond to a brother who is not following the authority of the word: Do not associate with him so that he will be ashamed, but do not regard him as an enemy but rather admonish him as a brother. The problem with too many is that they have no shame in cavorting with false teachers.
The principle is one of condoning (as Pickering aptly put it). When we associate by teaching/preaching or unified work, we are condoning what they do. When that involves a major area of doctrine, it is problemmatic. We can participate in their false doctrine (1 Tim 5; 2 John).
Let's face it: Most of us judge a church or group by who or what they associate with or have in to preach. That is why many conferences try to get big name speakers ... because it lends credibility. If you can get John MacArthur or John Piper or Rick Warren or any one of a host of others on your docket, your image is directly affected. Do we want to lend credibility to people like Jack Hayford? I can't see how ...