Wow, follow-up calls? That's a new one on me. I'll add it to my crappy recollection of how the story has progressed.
I cannot for one nanosecond imagine that MLK actually made such calls. Star Trek would have to be the absolute last thing on MLK's mind, even if he were a rabid fanboy like me.
I mean, seriously: the dude had the FBI investigating him and his ultimate murder wasn't a particularly big surprise given his massive following in what was at the time a very controversial social movement. I don't remember it except as history that I happened to live through, but I'd imagine it to be as much as surprise as if, say, Rush Limbaugh were murdered.
Too bad? Yes. A surprise? Not particularly. The dude must get multiple daily death threats.
Plus - while tne show did portary positive role models, the ratings for the network run were honestly pretty abismal. (EG In first run, not a lot of people were watching.) the success and acclaim Star Trek enjoyed came during the years in syndication many years after MLK's assasination. Hell, even GR himself abandoned the show after its second season, and sold the IP lock stock and barrel to Paramount shortly after the network run (but before the syndication run.)
My point? Why would MLK devote any time to worrying about an actor on a (at the time) failing TV series that no one is really watching?
Also, remember he was assasinated in April 1968. How much time did he have whith his schedule and other important issues to again, take time to check on one actor?