That's a good point, and one that destroys whatever moral high ground BLM might claim.
This is why gang crime carries more severe penalties.
That's the key right there. Is BLM a social movement, or is it a criminal gang (like the Mafia or the KKK)? Criminal organizations have only one goal, obviously a criminal one. Social movements have many goals, and subgroups might even have their own "unauthorized" goals.
To call BLM, as a whole, a criminal organization requires more evidence than I've seen so far. Now, if wiretaps of their leadership surface that show them planning criminal acts, my mind would change in a hurry.
Well if you look at their actions, many have been completely criminal and greatly endangering the public. Trespass, highway closures and the like. Then the frauds of their leadership. There is far more crime than social cause.