I got this from Reddit

One of the organizers of the event came over to me and said, 'Ms. Nichols, I hate to bother you just as you’re sitting down to dinner, but there’s someone here who wants very much to meet you. And he said to tell you that he is your biggest fan,'" Nichols said. "I said, 'Oh, certainly,' I stood up and turned around and who comes walking over towards me from about 10 or 15 feet, smiling that rare smile of his, is Dr. Martin Luther King. I remember saying to myself, 'Whoever that fan is, whoever that Trekkie is, it’ll have to wait because I have to meet Dr. Martin Luther King.' And he walks up to me and says, 'Yes, Ms. Nichols, I am your greatest fan.' You know I can talk, but all my mouth could do was open and close, open and close; I was so stunned."

Dr. King revealed to Nichols that TOS was the only show that he and his wife, Coretta, allowed their little children to stay up and watch. Further, he told Nichols what the show meant to him personally and detailed the importance of her having created a character with "dignity and knowledge." Nichols took it all in and finally said, “Thank you so much, Dr. King. I’m really going to miss my co-stars.” Dr. King's smile, Nichols recalled, vanished from his face.

"He said, 'What are you talking about?'" the actress explained. "I told him. He said, 'You cannot,' and so help me, this man practically repeated verbatim what Gene said. He said, 'Don’t you see what this man is doing, who has written this? This is the future. He has established us as we should be seen. Three hundred years from now, we are here. We are marching. And this is the first step. When we see you, we see ourselves, and we see ourselves as intelligent and beautiful and proud.' He goes on and I’m looking at him and my knees are buckling. I said, 'I…, I…' And he said, 'You turn on your television and the news comes on and you see us marching and peaceful, you see the peaceful civil disobedience, and you see the dogs and see the fire hoses, and we all know they cannot destroy us because we are there in the 23rd century.'

https://www.startrek.com/news/nichelle-nichols-remembers-dr-king