This is actually a popular misconception. MLK was just as radical as Malcolm X, it's just that his more radical writings and speeches are not as popular or quoted. Libs and conservatives both want you to believe that MLK was a reasonable progressive liberal, when in fact he despised them. I say this as a huge fan of both MLK and Malcolm X, and I had this explained to me initially by a professor of African American history at university.

Another way to say it is that every movement needs a carrot, a stick, and an ultimatum. The carrot is evangelizing the injustice (MLK), the stick is direct action (Malcolm X), and the ultimatum is an implicit show of force and dedication that demonstrates how many people will resort to the stick if the carrot is not accepted (the mach on Washington).

While I am nearly always in the peaceful outreach camp, I strongly suspect that my efforts will not see fruition until breathless WSJ editorials start describing environmentalists as "dangerous" and "unamerican."