If you start a sentence

with "I'm not racist but..." or "This may sound racist but..." There is a probability of approx. 123497348234% chance you should shut the hell up. How does that even sound good in your head? 
Just

Saying "I'm not racist but..." does not make whatever following comment more or less racist. It does not make you more or less racist. Saying "I'm not racist but..." is just a way for people to set up their incredibly racist comments while shielding/protecting themselves from the idea and fact that they are actually incredibly racist.

The best example right now could be the racist comments in politics about Obama. There are so many people---whether you, or even they acknowledge it or not, that do this all the time.

Twitter is the worst offender.

NOOOOOOOOOOO. For anyone who says that a person who makes comments like these isn't being racist, doesn't discriminate against Obama because of his color, they need to do some serious re-evaluating.

Think before you speak.