Just maybe,
When OJ was acquitted, it was perceived as Social Justice to potential rioters,
so when there was "Justice" in the verdict, the potential rioters were soothed into peaceful actions in "Rejoicing" over the verdict ?
So, if that's the case; rejoicing is directly correlated with individually perceived Justice, and rioting is directly correlated with individually perceived injustice.
Social Justice is Group
"Rejoice or Riot"