cause and effect of prejudice

This problem is happening as we speak. Although it is hidden behind expressions and words with other words sugar coding wat is really begining said, prejudice is still there. What cause this was back in slave years when white people thought that they were better then the rest of the population as they still do at this time. They use blacks and mexicans and also other populations to cater for their needs and they felt that other populations were weak and dumb. the effect of this called men and women like, MalcomX, Martin Luther King jr., Rosa parks etc, to rise up and take a stand against thses causes and show exactly why they were wrong and should be stopped. Although it still goes on until this day, it's not as bad and is however illegal to do. I feel that people who think that beinging prejudice was alright, should feel very ignorant for thinking so because they are showing how very cruel they are.