the content of their character

Do you know about Martin Luther King, Jr. ? I have ever heard about him when I am a high school student. I learned about him again yesterday in my university lecture. We listened his speech on August 28, 1963 at Lincoln Memorial, Washington, D.C. This speech is the most famous and titled "I HAVE A DREAM". He fought against racism and had this speech. I was touched to hear it. My most imopressive phrase is "the content of their character". This phrase is used like this in the speech "I have a dream that my four little children will one day live in a nation where they will not be judged by color of their skin, but by the content of their character." I think the most important thing to appraise someone is not a rank, not a honor, not a color of skin, but the content of their character. I got to want to know about him and Civil Rights. If you have idea about it and you know something about it, please give me a comment.