Oh please... the preaching get too hard?! A ton of other religions have standards concerning sexual relations... even within marriage. Plus, the Israelites, ALL 3 million of them (so a few hundred thousand) married couples did this and they were fine. Now, as for it being binding on NT believers, well I don't know about that, but I surely wouldn't have left. I would have listened dilligently, and studied like the Bereans did. I would have consulted with the pastor(s) and others. Who knows, maybe I'd be one who would "see the light" in this teaching. I haven't come across any of these people, and am not married and neither do I pastor married people (or anyone for that matter), so I have no need of this teaching, but that doesn't mean I'd just discard it.
Proverbs 18:13 says, "He that answereth a matter before he heareth it, it is folly and shame unto him." I'm not all for sticking with a church for anything, obviously, I'd leave for bad doctrine, but this is a standard, taught in sincerity and through study, deserves the consideration of those who are present at the study, and it can be studied, debated, ect...
GOD BLESS!
Bro. Alex