Seriously, I'm amazed how many people are ignorant of this fact. They didn't just blackmail him, they clearly implied that he should commit suicide before recieving the Nobel if he didn't want the tapes released. ("There is only one thing left for you to do. You know what it is.") They never released the tapes, of course, but he did die. Everyone also seems unaware that the King family was awarded $1 in damages from the federal government for the wrongful death of MLK; they contend that the US government assassinated him and used James Earl Ray as a patsy, and while they never got Ray's conviction overturned (despite trying) they did get a separate US court to agree that the government should pay them symbolic damages based on this interpretation of events.
Really, "that time the FBI tried to blackmail Martin Luther King into committing suicide" is too far back to count as an example of TLA overreach? We only know about that whole escapade because radicals physically broke into an FBI office and stole evidence of it, this isn't the kind of thing the government willingly admits to us. The CIA destroyed most of the MK-ULTRA documents when they realised Congress was getting ready to ask for them, but we still know that they were drugging unconsenting US citizens with LSD and secretly recording them having sex with hookers (they called it "Operation Midnight Climax") just to see what would happen, but I guess that's old news, too, or maybe it just isn't politcial enough to care about. We probably won't know that they killed Michael Hastings for another couple decades, and then that will be old news, too, so who cares?
