That's because points 1 and 3 were pretty bang on, in my opinion, and hence, I saw no reason to simply say "Yeah, I agree" without adding anything to the discussion.
You say that, yet your argument was focused on how casting characters of one ethnicity to play another hinders the overall vision of a film and as a result, the movie suffers in terms of an audience liking it. Coming back to your argument, I would first of all beg to differ. TLA has stayed within the top 3 ever since it was released a week ago. If the audience at large didn't like it, it wouldn't be able to maintain this; especially given its small in-built audience (nowhere as large as Twilight's or Toy Story's).
As for your comparison with LotR, there is a difference. It has been previously stated by Tolkien himself that he had intended Middle Earth to become an English mythology (due to his disappointment of a lack of original English mythology). Hence, the English-ness of its characters is an important factor. Airbender, on the other hand, while inspired by Asian cultures, is not about the characters' races but about a good story/adventure.
Overall, my stance on the race issue is that it is a non-issue. I do not find the practice of race-lifting problematic the same way I do not find the changes in plot significance/events in LotR since it isn't Tolkien's LotR but Peter Jackson's. Its keeping the LotR name is not a problem since it remains recognisable and true to the spirit of the original. The same can be said in this case.