When I first heard of BLM, I thought it was ridiculous to start that platform based on a case where a 17 year old went out of his way to attack someone (which he did, geometrically speaking, after walking past his own front door to go attack Zimmerman) and was killed in self-defense. The message I got from that loud and clear was that Martin's life mattered more than Zimmerman's because Zimmerman was being called white (when he's Peruvian). I didn't hear "black lives matter too," I heard "Trayvon's life matters more than the guy he went out of his way to beat the shit out of."
The Michael Brown case played out in a lot of the same way. BLM's message was that his life mattered more than the life of the store he just robbed and of the cop he just tried to attack.
By the time the Eric Garner case happened, which is the only one of the three that should have really deserved a movement, nobody gave a shit anymore about BLM because they saw people rioting and doing other dumb shit after the Trayvon and Michael Brown cases.