Not to detract from anything you wrote, just to provide some perspective.

Never try to defend a proposition against a hostile arguer.[2] They do not care. Your best arguments will fall on deaf ears. Your worst will be picked apart by people who are much better at this than you.

I have noticed a similar pattern right here on LW. If someone defends their "obviously wrong" beliefs, like religion or homeopathy or what have you, many people tend to ask them to explain, but only to cleverly strawman and pick apart their real or perceived erroneous arguments. Of course, when dealing with what Eliezer used to call a "settled issue" in this community, it is hard to give the other side a benefit of a doubt, given that they tend to rehash the same, or apparently the same, logic.

But if you flip the sides, it's basically the same, only more grave. Your religious parents know with absolute certainty that they are right. They know that you are misguided and that your feeble juvenile mind is corrupted. They have heard all the arguments you may present and rejected them as erroneous. It's a settled issue in their community. They feel responsible for you. If they are unable to save you and bring you back into the fold, they have failed as your parents. They have failed their God, they have failed their congregation and they have failed you. How can one expect them to engage you if not in the Hostile Arguer mode?