I don't know what to say about the Khan spoilers. But if this film is indeed intended for the Casual Fans who are looking forward to the new cast's adventures, but are still relatively new to the franchise, then I say the decision is fine. It's been 31 years since STII: The Wrath of Khan and that film timeless it might sound to us trekkies, It has aged alot.
I am disappointed at the sheer dislike this movie has received, even though spoilers don't reveal that much over how they execute the plot. But I am sure that people will complain about the pew pew
fast-paced action and not really focus on the fine little details.
About Khan's ethnicity... Like most others have said, Khan's character has evolved from what was once an experiment on Selective Breeding in "Space Seed", to a Genetic Enhanced Augment in TWoK. Certainly an update would be nice. And besides, we haven't seen how Benedict Cumberbatch acts into the role. We have seen Snippets, but not all.
Which leads me to say: The spoilers have made me want to watch more, because I want to SEE the execution of the film. I don't care how much some hardcore fans cry "BETRAYAL" when the film is made with Casual Viewers in mind, which are the majority and...wait for it...
The Needs of the many outweigh the needs of the few
JJ Abrams' Star Trek has a tough task of trying to appease both the casuals and the hardcore trekkies. In the end of the day though... I think your general reaction to the spoiler is a magnification of what you really feel for his franchise.