Why do people make racial slurs and gestures and believe that they are not racist?

Take for instance, the believed statements that all Black people eat fried chicken, that Asians (here in America) eat cats and dogs, and that Whites are all salad eating vegans. There are more, such as the ranking of I.Q. and personality. People believe that Blacks are dumb and ghetto, Asians are super smart and quiet, and that Whites are slightly higher than average and are completly innocent. These are just a few, but I'm sure you get the point. Anyway, people say these types of things all the time with absolutlely no second thoughts and when questioned, will not believe these are rasist remarks. Its amazing how people feed into sterotypes and even believe that they are not wrong or hurtful to say. I think it is the sheer ignorance of people. What are your thoughts on this?