Howard is responsible for his actions, of course. But you can't ignore that there are plenty of factions out there putting crap into people's heads...repetition, repetition, repetition. Eventually it becomes "fact". People soak a lot of it up...some more than others...and to different degrees. You can see it all around us. The Floyd case is a textbook example. Very few people take time to discover the facts...they just go with the repeated narrative.
So the question is...what happened to Howard? What/Who got into his head? As Whitlock says repeatedly...he was never this way before. Whether it was BLM specifically or not...who knows. But clearly something has changed the guy.