4) Why not start your search for the true essence in [....] Harry Potter?

Hm...

You went to great length there to show that ancient (pre-Hellenistic) religion was actually indistinguishable from culture. I absolutely love the description of the Old Testament as a "stream-of-consciousness culture dump", that's exactly what it is. But then you somehow go on to derive from this that it is incorrect that "religion cannot be proven or disproven". But if we agree that religion in antiquity was indistinguishable from culture, how are you going to defend that a culture can be "disproven"? Ancient Hebrew culture is just that, a culture, just like Aztec, Sioux, Celtic or Vedic culture. How are you going to "disprove" that? Except perhaps you are confusing "religion" and "theism", and suppose that theism is in some way central to religion. But then you should say theism, which is completely detached from picturesque Iron Age culturescapes. For theism, you should focus on Hellenistic and Roman authors, who said intelligent tihngs such as "credo quia absurdum". You aren't going to "disprove" Augustine by making fun of Elijah. But while you focus on theism, you should make very sure not to confuse "theism" with "contemporary naive US Bible-thumping". It is a great fallacy in much of what I read from US atheists that they tend to equate "religion" with "theism", "theism" with "monotheism" and "monotheism" with "braindead biblical literalism".

I understand that much of US atheism is tied up in fighting a political war against conservative bible-thumpers. But it is a bad sign if people start confusing this political war with actual religious philosophy. So you wish for a society where there is a notion of "marriage" based on the historical institution known by that name, but both separate from religion and detached from the sex or gender of those choosing to register. This is of course your right, and within your powers you can exert influence that may or may not result in your desired outcome. But nothing about this changes the fact that the word "marriage" historically describes an institution that very much depended on both sex and religion. And accepting religion as a simple historical and ethnological given, I frankly don't see any room to "disprove" anything about it: You are perfectly free to disapprove, but that's not the same as disproving anything. Oh, by "disprove" you mean you do not believe that the world's myths are factual records of historical events? I don't know how the Iron Age Hebrew priesthood would have reacted to this idea, but every intelligent religionist from Plato onward would just have smiled at your naivete. Yes, there are the less intelligent religionists, like, say, Torquemada or Jack Chick, but if you are interested in criticizing a philosophy, shouldn't you out of intellectual integrity talk to its most intelligent proponents instead of having a field day with the idiots in its camp?

Why can't modern Nazis disavow ancient Nazi practice in favor of some true essence that makes sense in modern terms?

One can argue that holocaust denial is an attempt to bring nazism closer to modern ethical values. Real, authentic Nazis were proud of their achievement and would be outraged by thought that their successors would call them a lie.

Why not start your search for the true essence in Lord of the Rings

Some people do :-P

Why not start your search for the true essence in Lord of the Rings, which dominates the Bible both ethically and aesthetically? Or Harry Potter? Or Oh My Goddess?

Because we have Atlas Shrugged :)

For number 3, I realize the implied point, and I assume that there is more to this argument, but that sentence was one big strawman. Also, I would respond by asking why someone following the 'true essence' but confirming to modern societal/ethical norms is any worse than someone who is following said norms for a different reason. For #4, those novels don't explicitly provide ethical direction-one can use a system of ethical precepts without it being absolute and unchangeable.

3) Nazism would have been unexceptional if it had been an ancient religion instead of a modern government. Why can't modern Nazis disavow ancient Nazi practice in favor of some true essence that makes sense in modern terms?

Just highlighting this point.

Room full of first year pedagogy students, lecturer puts a claim "marxism is not the philosophy of Marx." He explains how marxists distorted original Marx' thought and how the original claims are so great and describe the world and how they should be followed.

If I was generous, I would say he wanted the students to argue, he wanted them to think critically and disprove his weak argument, but he had experience with students and those were 18-year-olds, who would always try to shut down my questions for explanations "because we want to have this lecture finished". The way it worked, for next two weeks all girls in my group (exept for one other older student) were avid, bona fide marxists. And likely spread this ideology to their families.

3 is happening in real life.