As time goes on, MLK's message and his quotes are going to morph to fit the popular viewpoint. That's just how history works. Even with video proof, someone can place a quote in a different context and change its meaning. We truly live in a post-fact world and the scary thing is maybe we always did.
People often like to paint a picture of a person after the fact that is different than what the person stood for or what the person actually said. For this reason, it's important to look at all of Martin Luther King's message. There is no way to understand MLK without understanding all of the perspectives he had.
Our society has not ignored large pasts of Martin Luther King's message. King advocated non-violence and peaceful protests in order to enact change. King's message was heard by a majority of society; and changes did take affect in a non-violent way. More people today should follow King's message of using peaceful protests to advance their causes.
I believe that not all of MLK's messages made it into the mainstream, but this can be said of many famous individuals. MLK was ahead of his time and typically views from people of his caliber can appear to be radical. The most important messages from MLK have been kept and that is all that matters.