For some people the primary social contact that is broken is long running systemic racism.
For some it's militarization of the police.
For some it's the US seemingly slowly sliding in facism
For some it's the economic Injustice of being told "the economy", i.e. the stock market is doing great while unemployment is at an all time high.
Etc
This strikes me as too simplistic solution. I tried to find papers on how demonstrations become riots, but my google.scholar-fu has failed. Anyone got good review papers on this? (If none exist, there is a goldmine there for social scientists.)