Martin Luther King, in my opinion, was in fact a good and decent man. He was completely against slavery and discrimination. Naturally, I understand times were much different during his day, but when I think about it, he had very good points, and a very positive way of going about them.
Martin Luther stood up to corruption in the church and introduced the reality that sins could not be cleansed by monetary donations to the priest or church. This was a brave thing for him to do. He may not have been accepting all around of others, namely the Jews, however this is due to his strong convictions about Christ. Martin Luther stood up to church hierarchy and stood for the people, the Christians, who were being taken advantage of by their church, and led to the protestant reformation. Martin Luther was a great man.
To be fair, I don't want to say anything about a person I don't know personally, but I don't know. Something in my mind associates his ideas with the Ku Klux Klan. I mean maybe it's not true, but he could have a been a racist himself. All I know is many of these Lutheran countries engaged in violent imperialism (England under the Georgian kings [first two], Denmark, Sweden).