As to the argument about why one stays - I believe it is an argument similar to Henry Ford's quote "Whether you think you can, or think you can't, you're right."
Because opposition in all things is a feature of God's plan, I believe both "culture" and "truth" should be taught (not by the same person of course, each has its own prophets).
But I believe only one of them leads back to God and increases faith in Christ.
To me, teaching that culture is the reason people leave makes you a false prophet because it cedes as legitimate a false teaching that we are not agents to act for ourselves. It changes the gospel from an outward "how do I treat others" to an inward "how do others treat me." And even when viewed on behalf of someone else shows you would rather be judge than rely on and teach the power of the atonement of Jesus Christ to heal. It should not be justified. It is false because it scapegoats "culture" for the true culprit "lack of faith."
Any true prophet will teach that seeking truth, trusting in God, and enduring despite all else will lead you to stand independent of all else (your faithfulness will not and does not have to rely on anyone except Christ).
So why do I think both should be taught (again, by their own prophets)? Because this life is a test. God wants you to be exposed to truth and falsehood to see which you want. Do you want to blame others for your choices? Great. Now he knows you don't want to be like Him and he knows more about what glory you do actually want. That is how/why everyone will/must confess that his judgements are just.