The Civil Rights Movement of Dr. King's era: Successfully ended Segregation in schools and public areas, paved the way for activism for decades to come, to the point where Minorities are able to amass wealth, personal success, and are represented in media in regularity.

Social Justice Era/ #BlackLivesMatter Era "Activism": Directly responsible for the worst race relations we've had since Dr. King's time due to undue aggression combined with a refusal to point them at any of the culprits actually responsible for the injustice they claim to fight against, refuses to take any responsibility for damages caused from their "peaceful protesting", often and shamelessly targets other minority groups while claiming to act in their interest, silences all criticism as racism and "Coonery", long since abandoned undeniable victims of police brutality (Tamir Rice, Freddie Gray, Eric Garner) in favor of actual thugs that no one would really be willing to die for (that one jackass who knocked up a 14 year old girl and refused to pay child support) and perpetuating hoaxes like Mizzou and zero empathy for any tragedy they can't exploit (ie the 2015 France terrorist attacks).

Ah yes, I have heard of that quote, "Riots are the language of the unheard." I can also agree with your assessment on MLK's feelings, but I also want to add this tidbit to what you have said:

Likening riots to an "emotional catharsis" I feel is quite apt: people are angry so they destroy. It's pent up frustration. Yeah, okay. I can get that. But he also points out about how futile it is in the end. If I had to make a comparison, I would say a riot is like punching a hole in the wall of your house after being laid off from work. Sure, you might feel a little better letting out your aggression but you didn't solve the problem and now you have a hole in your wall.

That's just what I think he means. I'm no genius, but just my two cents.