There are very few blacks in Seattle. They represent around 3% of the population. These are white anarchists.
There may be some method to this madness If property values can be depressed, people may decide to get out of town. Many may end up upside down on their mortgages, as in the sub-prime crisis. A couple of houses full of anarchists in a neighborhood might be enough to discourage more neighbors. De-gentrification would ensue.
Nevertheless, in the end all blacks are going to get the blame for what these white anarchists are doing unless a sufficient number of them vocally denounce the rioting.
Now, suppose you’re a responsible black person, do you really want to get in the sights of BLM? I’m guessing they hate responsible black people even more than they hate white people.