Martin Luther King, Jr. is a beloved icon and looked up to for his work defending Civil Rights. His beautiful speeches and peaceful methods were a sea change in the movement. He stood out in a world ruled by angry, racist white men. If he was more radical than we learned in school, then one can hardly blame him.
MLK's views and ideas were very radical in the 1960's. Most forward-thinking individuals have radical views that help speed up changes in society for the better. In the 1960's, all people created equal was not fully accepted so it would come off as a radical idea. Much of what MLK stood for then is the norm now.
It is always interesting examining the historical record. Everyone always associates MLK with peaceful resistance and civil disobedience, and associates Malcolm X with radicalism and violence. This is accurate from their early writings and speeches. However, examining the pair's words and writings from later on in their lives is interesting, as we see a shift. True, MLK was never as radical as early Malcolm X, and Malcolm X was never as peaceful as early MLK, but they ended a lot closer in viewpoint than anyone cares to admit.
There is a good reason that the media avoids those nine quotes from MLK. They don't allow the media to paint the narrative of MLK that they want to paint. They don't want anyone to be able to question MLK's message or what he stood for, so they filter some of his more controversial things.