I don't know why some Republicans are acting surprised.
Your base is primarily poor trailer trash white Americans who want America to go back to the 1800s so they can compensate by treating minorities like shit. They never supported the police or the government, they just supported them when they were shooting black people down. And now it's evident with the way they get to be "patriots" instead of rioters or domestic terrorists.
You don't need to support BLM to realize the difference in treatment.