Films reflect the society in which they're made, no matter what they're based on. Don't the fans have more to annoy them than a few "ethnic" hobbits?
Damn, practically every famous "human" Disney hero ever made is 100% white cornbread American (Aladdin, John Smith, Hercules, etc) whereas their antagonists are almost uniformly of "ethnic minority". (I'd love to meet the soulless Disney beancounter-turned-creative who thought to himself: "Hey, we need a way to make Scar obviously different to the other lions. I got it! Let's give him a darker coat and a British accent!" And then shake him by the neck until his teeth fall out.)
And nobody seems to have a problem with this (presumably because Jeremy Irons is pure distilled awesome, and the list of Disney Villains he's played has kept him working for years when other, better roles were hard to come by.) But the moment you mention brown-skinned hobbits, everybody goes NUTS!!!
What next, black people, not playing slaves, in a Jane Austen adaptation? THE HORROR!
**(I should add a strong "sarcasm warning" to this post, on account of a lot of extremely thick people will inevitably misinterprit it and accuse me of being a vile minority-hating Nazi; something that seems to happen with monotonous regularity these days. If you were thinking about "calling me out", withdraw your bows, uncock your pistols, and consider yourself suitably chastised.)