Was MLK “the most dangerous and effective Negro leader in the country” ?

Hello all ATSers, I've been lurking for sometime now and this is my first post so if this is in the wrong place please forgive me!

Anywho, Acording to a 1963 FBI memo Dr. King is stated to be the “most dangerous and effective Negro leader in the country”. Question, why is it that any person or organization is deemed a threat by the United States Government if they try to incurrage growth, spread knowledge and uplift the people? Just like with Bob Marley, “deemed a threat” great men in search for peace.

Anybody that could trigger an upheaval in the established social political order is perceived as a threat. Makes you wonder if people like John Lennon stayed around how the world would be a different place.