And it's not even relevant anyways. You might as well say they're anti-vaxxers. I don't support BLM for its global economic policies, assuming they even exist. It's not like we have a choice between voting in the BLM Party or the Conservatives in the next election.
My suspicion is this label has been foisted on them by the right as a means of discrediting them. It's an old play and its effective inasmuch as it works on people who want an excuse not to support equality.