I think MLK was talking about the inevitability of violence as a result of a lack of progress, rather than "validity".

As for last summer's BLM riots, they were little more than a Democrat PR exercise (witness BLM's use of the "Act Blue" fundraising platform), and a chance for white college kids to virtue signal for the sake of YouTube livestreams. It's a shame that the black community seems so willing to whore out its historical suffering for the sake of a presidential candidate of any stripe, as well as allow it to be used to further the ambitions of a failed political ideology (Marxism).

If you want to see just how shallow white liberals are when it comes to race, just watch them circle the wagons when a black man runs for office as a Republican. (Hello, Larry Elder.)

Since the BLM riots, all I've seen on this and other platforms is the narcissism of identity politics. (On Medium in particular, virtually all "racial justice" articles I've seen are of the "omigod, white people are so annoying!" variety, and absolutely nothing that addresses the cold, hard economics that are at the heart of black inequality.)