It depends on the context. Specifically when it comes to racial injustice, personally, I am okay with targeted looting/vandalism. When rioters burned the 3rd precinct in Minneapolis, I thought that was an important, symbolic message to send. When Target refused to sell milk to protestors who were tear gassed, and were subsequently looted, I fully supported that. I think looting and vandalism should be targeted toward entities that are complicit in perpetuating the injustice minority communities suffer through. That's fair game. I don't support mindless looting and destruction, though, where your target has no strategic purpose.
Though, while in the abstract I don't support *random* looting and vandalism, I think it's important to take into consideration these things are symptoms of grief and rage. No one should be surprised that oppressed communities have pent up anger and resentment, and that reaches a flash point when a trigger event occurs. It's like if my parents died in a car crash and I became an insufferable drunk, people may not like it, but you should be able to understand and sympathize with it.
I feel like it's unfair to harshly criticize protestors participating in this kind of action for "making the movement look bad" because most of the time, as I said, it's not strategic or calculated, it's a grief response. If you don't want people to riot, you should fix the circumstances that are causing them to riot in the first place. It's really backwards to express moral outrage at the *symptom* of a larger problem.
If I were a king and I starved half my populace, and they started to riot and burn things, and started slaughtering loyalists in the streets, yes you could make the argument it isn't necessarily moral but Jesus Christ, who's really at fault and responsible for the situation? Me, the king.
Ofcoooooooourse, people are going to riot and burn **** when their brothers, sisters, mothers, etc. are being shot, beaten, brutalized, etc. and they never receive any justice. Honestly, I'm surprised they haven't tried to bomb state capitol buildings and other government facilities the way the U.S
government treats its citizens, let alone minorities.
Imagine if the French government pulled half the **** the U.S. gets away with. The populace there would wipe out their elected leaders entire bloodlines. Part of the reason why this nonsense is allowed to continue without end is precisely because we aren't rioting and burning **** down *enough* We have an extremely complacent and tame populace compared to citizens of others nations that demand better.