The public has been effectively propagandized and made to turn against one another rather than a corrupt system. If you accept the thesis that endemic racism and corruption in the American justice system exists, that the reason for the anger behind these riots and protests is legitimate, then your personal ideological polarity shouldn't matter.
Unfortunately, it's easy to get people to dismiss the movement wholesale by associating it with the specter of Marxists and Angry Black Men.
And that still leaves reasonable demands being ignored. If you don't support completely defunding and disbanding the police, you could agree that de-escalation training and shifting of funding priorities might be effective. That doesn't need to be slotted into a left-wing political agenda.
>Secondly, many BLM protestors are clearly brandishing symbols that are associated with Marxist/Communist ideology, many self-identify as "Marxist", and even officially they refer to each other as "comrades":
And a lot of BLM protestors, likely a large majority, aren't and don't. There's a difference between some Marxists supporting the movement and the movement itself being Marxist or having a Marxist intent. Black Lives Matter is clearly not about Marxism.