If you accept the premise that all cops are racist white men, conspiring to shoot as many little black boys as possible, the BLM thing is easy to sympathize with. But, of course, that would make you an ignorant Fake Sugar Dick (WARNING, NOT THE REAL SUGAR DICK!).
No particular race is more likely to be killed by a cop than another. There are tens of millions of civilian police interactions every month. A black and a white guy each have less than a .001% of being killed in those interactions.
I would imagine the demographics of the people killed generally aligns with the demographics of the people incarcerated for committing violent crimes.