There was nothing normal about the whole movement that MLK Jr led. He presented himself as a holy man while participating in rape.
His close advisors included major organizers of the Communist Party. And this was at the height of the Cold War. The steelman argument for the FBI's decision is that it faced an extraordinary threat to national security in the person of MLK and resorted to extraordinary measures to try to neutralize that threat. And as far as the FBI went there were certainly lines that the FBI wouldn't cross.
There are also, of course, very strong arguments against the FBI's covert action against King, and those are well-known.
> There was nothing normal about the whole movement that MLK Jr led.
I agree; racial equality was a new idea for the USA. Really weird. Totally against the status quo.
> He presented himself as a holy man while participating in rape.
He presented himself as a reverend and also a civil rights leader. He was both. You make it sound like he wanted us to worship him. Nothing like that.
Racial equality was established over a course of a century, from the Civil War onward, through numerous Supreme Court decisions (e.g. the 1920s rulings which outlawed racial restrictions on voting, and Brown vs Board of Education in 1954 on the separate but equal clause) that abolished institutional racism. By the time King began his movements, most (though not all) elements of institutional racism had been abolished.
As just as King's cause was in many respects, using powerful national movements to essentially cripple localities to force them to bend to the mass-movement's will held enormous destructive potential, especially with King's ties to the Communist party.
A reverend is a holy man. Being one is entirely inconsistent with how King led his life.