BTW, I wonder what will happen when ROTK premieres and people realize that all the Bad Men have dark skins? If he stays true to The Book.
Not actually true; they are allies of Sauron, but as you recall from the Oliphaunt scene, Sam speculates whether they were forced to come and fight for Sauron. It's not clear at all that these people are evil.
Also, there are plenty of "whites" who are on the wrong side...Dunlendings fighting for Sauruman (although I hear no mention of them in TTT coming soon? Has Peter Jackson elminated them?)....the wraiths who Aragorn calls to fulfill their oaths...the "black" Numenoreans who go over to the service of Sauron, etc.
You're right. Except there are several other places in Tolkien where the Southern peoples are portrayed as being peculiarly prone to Sauron's influence. Couldn't give you chapter and verse, but it's in there.
He makes a big thing about how (for the most part) only the Edain and their relatives (the Northern peoples) are resistant to evil. That's over the entire 6000 years or so covered in his history, so it starts to look a lot like a genetic type of thing.
Only about half the Men in Sauron's army are Southerners. The rest are from the East. The only thing I remember about them is they tend to fight with axes and wear beards. Nothing about skin color.
BTW. From what I hear, they are going to portray Saruman's attack on Rohan as a genocidal war to exterminate humans. If Dunlendings make up a big chunk of his army, it kind of puts a crimp in this storyline.