Black lives matter doesn't mean all othe lives don't. Imagine for a moment that you broke your left wrist. In excruciating pain, you rush to the emergency room for treatment only to run into a doctor who insists on examining not just your mangled left wrist, but your uninjured right wrist, rib cage, femur, fibula, sacrum, humerus, phalanges, the whole bag of bones that is you. You say, "Doc, it's just my left wrist that hurts." And she says, "Hey, all bones matter."
If you understand why that remark would be factual, yet also fatuous, silly, patronizing and off point, then you should understand why "All lives matter" is the same. It's not about "elevating some lives" any more than it would be about elevating some bones. Rather, it's about treating where it hurts.