Discriminate (verb) - to recognize or perceive the difference, marked by the ability to see or make fine distinctions.
Yeah. That's what casting agents do for a living. I can't get a job playing a buff action hero in a Hollywood blockbuster because I'm pasty and overweight. It'd never play, so I don't get the part because its largely recognized that there are certain archetypes for these parts, and I don't fit them.
Playing devil's advocate, though, the Shire has always been that place of ideal, innocent (near ignorant) living. In contrast to the "outside world", which is consumed with warfare, politics, and strife, the Shire is meant to serve as that beacon of hope to the characters and the audience familiar with it. It also makes a good start to "the hero's journey" and the character growth contained therein.
It actually makes more sense to me to have multi-cultural hobbits in this regard. I personally believe that society will never be rid of prejudice (I'm not going into my opinion on this further, but it stems from conflict and social identity theories in sociology and psychology). Because of this, a multi-cultural utopia is perfect for the Shire. Particularly when we get to compare it to the racism inherent at the end of the book, where lines are drawn between Dwarves, Elves, and Men who are all competing for the wealth left in the dragon's hoard.
I'm not sure if the director considered this angle, but it's an interesting enough premise that I would support any endeavor to do so. Even if it meant a slight departure from the source material I love.