First of all, Kenny isn't racist. "Urban" was just a nice way to say it. However, consider the news (Media-wise), I don't know about you all, but 90% of the time, when a crime is committed, it's an "Urban" person. Am I racist? No (Heck, I dated an "Urban" woman for a while. The eating pig's feet thing was kind of weird, though. :/). Is this just a sad truth? Pretty much. Don't get me wrong, I know a lot of folks who are "Urban" and made a good life for themselves, it's just a majority when you watch the news, or read the paper. Just a sad truth. It's easy to see how people could get that frame of mind.
Odd couples are everywhere (Look at myself and the "Urban" girl.

). In some instances, opposites attract. We don't actually get to see how they met, or what drove them to the point of marriage. I actually think Kenny and Kat made a good couple. They accented themselves, to some extent. Kenny was the aggressor of the relationship and Kat was his balance, keeping a cool head and open mind.
I will agree, though, that although opposites, I just can't see Christa and Omid working it out. Though, implied through the game, they do seem to have a decent relationship.

Go figure. :P