What communist leanings? My understanding is that he had none, and that this was just made up by people who disliked King for other reasons. A bit of Googling corroborates this [1], but if there's evidence I'd be curious to hear it.

If King's "communist leanings" didn't exist then they could hardly have been "the main reason for wire-tapping him" or indeed the reason for anything at all. Something non-existent can't provide any "historical context" either.

I think the context you're trying to draw leads in fact to the opposite conclusion. "Suspicion of communism" then equals "suspicion of terrorism" now, and what the story shows is how easily these powers become abused. "Suspicion of X" is a self-confirming charge after all.

Edit: I also think you're really stretching things to argue that Hoover going after King was "the government executing the will of the people".

1. http://www.snopes.com/history/american/mlking.asp. The email circular at the top of that page indicates the quality of thinking among some people who like to believe in King's "communist leanings". Thanks to Google I've just learned that there's a whole world in which this is still a thing: http://www.martinlutherking.org/thebeast.html.