It's communism. Cold War. All there is to it. As with much other evil, this was done because the FBI feared that Big Bad Uncle Ivan will somehow gain influence over this leader and use it for leverage in the Cold War.
The same multitudes of extramarital affairs and other racy and embarrassing stuff that Dr King took part in, as a reverend, could be used by communists to blackmail him into working for them or making decisions that favour the Soviet Union. Is it far-fetched? Sure. Is it, in hindsight, paranoid and stupid? Yep. But can we say with certainty, without hindsight, that it was impossible, when you have an entire organization dedicated to rooting out hidden influence of the enemy in an existential covert global struggle?
And it wasn't all paranoia. The Soviet Union under Stalin was extremely good at infiltrating American academia, civil society and government. The Rosenbergs, Alger Hiss, Harry Dexter White, etc. The US government went from ignoring the problem and dealing with it so incompetently actual Soviet spies were in almost cabinet-level positions, to hysterically over-reacting and ruining the lives of people like Dr King "just in case".
[–] DFHippie 15 hours ago
(well, the Russian Federation, not the USSR)
[–] cowlevel 15 hours ago
[–] kspacewalk2 15 hours ago
[–] jackb4040 15 hours ago
[–] kspacewalk2 14 hours ago
[–] ricksunny 14 hours ago