The best example I've seen yet, that illustrates why the Black Lives Matter message is important and distinct from saying "All lives matter" in a just way went something like this (paraphrased from memory, and elaborated/expanded from my imagination):
Person: That house is on fire, somebody should do something.
Person2: What about those other houses? They could catch on fire someday as well? Isn't it discriminatory to focus on this one house? All Houses Matter
Person: Yes, all houses matter but this house is on fire Right Now. It needs immediate and specific attention.
Person2: What do you have against those other houses? They are made of wood and they are capable of burning as well.
Person: Are any of them ON FIRE RIGHT NOW?
Person2: No, but they can catch on fire and some of them probably will one day. We should think about all houses and mandate residential sprinklers in future homes.
Person: YES, but RIGHT NOW this house is ON FIRE and somebody should call 911 so they can put the fire out RIGHT NOW.
Person2: Why is this house so much more valuable than all the other houses? What about all of the other houses that have burned down?
Person: Aaargghgghghg!!!!!!!
