The point of BLM is equality, not racism. You can't piss on the whole movement because of a few asshats who align themselves with it.
It is not accurate to compare a white supremacy to blm.
Equality means people can indeed piss on the whole movement because of a few asshats who align themselves with it.
That is what mainstream politics and the press do to these sorts of political movements. That's what they did to the Tea Party, Occupy Movement, and now Black Lives Matter. Guilt by association is a pretty transparent tactic by parties aligned with various factions to undermine competing factions. And guilt by association in particular is the inherent weakness of populist movements because populist movements by their nature are going to include many many more people with a wider range of backgrounds including racists, criminals, gang members etc etc. There is simply no way to defend the integrity of a populist movement based on the integrity of all of its members.
It is also the weakness of BLM in particular because the movement has no simply stated achievable goals and relies on a shared sense of oppression and persecution for an ongoing sense of purpose. And there has been, a now exposed, cynical conspiracy by the democratic party elite to co-opt black lives matter into a vehicle to drive turnout on election day without actually delivering any achievable policy... Keep it supportive yet vague was the directive.
Again the cynical democratic party elite has tried to make sure BLM has no clear achievable agenda other than being a vehicle for discontent. The implication being that any actual policy agenda will either be too divisive within the democratic party or will be agreeable to all sides and won't allow for a contrast between parties that would help drive turnout.
It simply doesn't serve the party to achieve anything before election day other than black voter turnout. And then the next election is just two years away... It is up to BLM leaders to get some agenda on the table that most people can agree to and to stop being used for petty partisan politics. BLM itself needs to keep the focus on the things that can actually work to make things better.