How do you sensor what you say?

What makes people sensor what they say to other people? On that note, what makes people think it is ok to say politically incorrect things to "almost" complete strangers?

I walk my dog at the park near my house. Because I always walk around the same time of day, I tend to run into the same group of people. Most of these people I know nothing more about them than their dog's name(s). Even though I see these people day in and day out for the better part of 2 years, I do not know anything about them. On that note, while I am not registered to vote, I definitely classify myself as a liberal democrat. Although my political beliefs and feelings about certain people in certain important positions who got this country into a war that is headed down the road of another politically controversial and senseless war that lasted for years upon years, I don't go spouting my political or social beliefs to strangers. In fact I rarely talk politics or make social commentaries unless you know me very well.

This leads me to Sat. morning. I was out walking my dog and ran into this older guy that I "know" (as in I know his name and his dog's name, and I know that he is ok with me having my dog off the lease) (and he is really old, like probably in his 70's). He's nice enough and in general he is very nice guy to talk to while you are wandering around the park. Saturday morning we were standing there talking and an African American guy goes jogging by us. Mind you he jogged by us and jogged up a hill that I can barely drag myself up at a turtle pace, let alone JOG up. The older guy I was chatting with responds with the following..."That reminds me of a joke (at this point in time I have no idea what reminded him of the 'joke' he is about to tell)...Why doesn't Mexico ever have track & field athletes in the Olympics?" Seriously, did he just say that? Since I can barely understand why he would tell this 'joke' to someone he barely knows, I utter "ummm, no, don't know". He responds "Because any of the Mexicans that can run or jump have already left the country." Ok, for a racist joke it is kind of funny but regardless, it is a racist joke. What makes a person think it is ok to go around saying things like this to people they barely know.

Now mind you I am not the kind of person that thinks that we can create a world where racism doesn't exist. I am a realist and realize that there are people that will always believe that they are better than someone else, purely based on the color of their skin. I also realize that make racial stereotypes have a lot of factual origin. But I also believe that anyone with the least bit of social or political sense knows that even if they hold those beliefs, they censor their own thoughts until they know how and if a person they barely know will react to a 'joke' like that.