I used to think it was ok to say "all lives matter" but I've come to realize it sounds really snarky. The 'Black Lives Matter' movement has organized to protest injustice and inequality, and if people outside the movement say, "but all lives matter" it kind of negates all their work while horning in on their successes.
The organization sees that there's inequality and they want it rectified. It's their movement. I'm in favor of equality and as long as they are not doing anything illegal let them have their successes. I hope they are not behind the riots.