Assalamualaikum!! Well, there's no law against posting in Arabic or attaching it to riot gear. Maybe, just maybe the poster is ensuring that Muslims are able to read the message. Yes? Maybe they should also write in Spanish, Asian, Russian, etc. to ensure that everybody know what's up. I have a confession:

Black lives prolly don't matter, and, haven't mattered since...well, forever. Have a stroll through the following pictures in the link provided.

https://www.facebook.com/MuseunofLynching/photos/pb.380294642090237.-2207520000.1457312395./811399058979791/?type=3&theater


It's only more sophisticated and subtle to an extent now.