The case against King was a little more specific than that, though still not a reasonable basis for suspicion: One of his close associates had historical ties

The case against King was a little more specific than that, though still not a reasonable basis for suspicion: One of his close associates had historical ties to the US communist party. It was such a weak case that Hoover had to really push on LBJ to let him go after King so aggressively, and probably reflected cryptic racism as much as his fear of communism.