Everyone I know thought it would win for that reason. Same reason Crash won and crash wasn't a great movie.
Everyone you know has terrible taste in movies than. It was up against a number of great and creative movies. Personally I was pulling for Nebraska to win but knew it wouldn't because the academy doesn't give best picture to comedies pretty much ever.
Crash won because it was in a really weak year. If it was up in 04, 06, or 07 it wouldn't have won, regardless of the "PC" aspect.
If the "PC" movies won all of the time why did Hurt Locker beat out precious, the Blind Side, and District 9. Why did the Artist beat out the Help? Why did Million DOllar Baby beat out Ray?
BTW I'm just assuming when you say PC you're talking about movies that portray black people in a good light.
12 years a slave won because it was universally loved by critics, 97% Metacritic score, and it was the only movie that was that highly rated and fit into the likely to win categories. THe more comedic, Her, American Hustle, and Nebraska didn't have much of a chance. Gravity had almost a 0% chance (return of the king is the only Fantasy best oscar winner, no Sci-Fi best winners)
I am curious though, what movie do you think was a slam dunk winner over crash? I would have given it to Capote, and the "PC" choice to me would have been Brokeback Mountain. I'm guessing you would say Munich, which wasn't any better than Crash.
Crash was a good movie, but again, it went up in a weak year, put that up against The Departed, No Country for Old Men, Million Dollar Baby, etc. and it loses whether you think it wouldn't because of being "PC"