I searched for a long time looking for this sermon from Martin Luther King Jr. online and at the King Center in Atlanta. I am sorry to report that his speeches and sermons don't appear to be centralized anywhere. I found some resources at Stanford's website via The King Papers Project.
I wanted to share the audio of an awesome sermon with you, but instead I am forced to leave you the information only.
In the sermon below, Dr. King talked about "good hair". He addressing the congregation referenced his hair being good, that he washes it, combs it; and that we as a people should accept our natural hair as good also.
"What Are Your New Year's Resolutions?, Sermon delivered at Ebenezer Baptist Church." 1/7/68.
Photo coutesy of the US Library of Congress.