Taboos around violence for political are one of the crucial building blocks for a functioning democracy. If those taboos are broken, even for a good cause, you set a precedence that violence works. And the next cause won’t be as good. One only has to look at the lessons of the Roman Revolution that started with the murder of Grachus, and ended with an Emperor who everyone acclaimed as they were so tired of the bloodshed.
The non-violent protests of Colin Kaepernick were mocked and used to rally the other side and just weren't effective.
The problem here is not the violence, but a policing system that is so fundamentally damaged and has not been effectively reformed fast enough.
The MLK quote is trotted out pretty often, but "a riot is the language of the unheard".
Even if so, 90% of the protests and property damage were after the arrest, so... they're pointless?
The other three cops who helped to kill George Floyd have not been charged or arrested. Neither have the men who killed Breonna Taylor. That's hardly the limit of police violence that has gone unaccounted for. At this point it’s more of a protest against police brutality than just the one specific murder. So, no, not pointless.