Something to consider is that the left has basically turned on MLK. They reject his idea of ~content of character~ mattering more than skin color. They want factionalized racial politics and MLK’s message conflicts with that. I could imagine many on the left delighting in seeing his reputation destroyed, because it would also mean the destruction of his idea. You're exactly right. MLK's message on race-relations is now our message, and trashing him is trashing a guy whose speeches on race should be one of our most effective tools to expose the race-baiters.