"I'm not one of those politically-correct folks..."

Why is it so many like to say they're politically incorrect? After uttering something which only a handful of people the world over might find offensive, they'll say, "I'm not one of those politically-correct folks." It almost comes across like a hybrid of bragging and a just-in-case defense: "Yeah, I'm a bad boy, but if you are offended, I didn't really mean anything by it."

My issue with any such statement is, if the person truly is what they say they are, why do they feel the need to say it? "I'm not a racist, but..." Okay, good, but if you're not a racist, why do you feel the need to tell those around you? "I'm not a sexist, but..." That's fantastic, but why do I get the hunch you're about to say something sexist, making your claim moot? "I'm not one of those politically-correct folks..." In this case, at least the person is being honest (to a certain degree), but still, what's the point in saying it? If a person continually makes statements which are regarded as politically incorrect, there's no reason to say, "I'm not politically correct." If I have a one-track mind when it comes to math and following 30 minutes of math jabber I say, "I like math," the chances are high I'll receive looks which say, "Well, no sh*t there, Sherlock." 

All kidding aside, I think people do this as a just-in-case defense. In case someone in the group gets offended by their comments, this somehow provides them with a valid excuse. It reminds me of the line, "No offense...," as if telling a person "no offense" will somehow negate the emotion they feel when hearing the offensive comment(s). Look, I often write comedy, so it's virtually impossible for me to be "politically correct" 100% of the time, and due to that, it's next to impossible for me to not offend at least one person every time a piece of mine gets published, but I still appreciate and value political correctness to a certain extent, as I think everyone should be seen and treated as equals. Having said all that, though, if a person is about to utter a line so offensive they feel the need to provide themselves with the just-in-case defense of "I'm not one of those politically-correct folks...," perhaps they should think twice before uttering such a statement.