Racist!!!! ;) kidding!
I think the main problem is that BLM stands for many different things it is open to interpretation. Good people who are just seeking justice and reform can use it while at the same time bad people who just want to cause trouble and burn down the world can also use it. Mixing peace seekers and rioters into the same "protest" essentially turns the peacefull people's message into rioting. Then since all people see is the bad stuff happening all BLM becomes "about riots".
The joys of having a semi decentralized structure! BLM probably has more peaceful protesters in it than rioters. I haven't tried to delve into the numbers though so I could be wrong.