That is not not always true, it depends on how much the poor have been oppressed and what they are willing to do to end that oppression.
French Revolution ( https://en.wikipedia.org/wiki/French_Revolution ) 1789, the poor class basically killed the entire rich class, it took many years but they did it.

Boston Tea Party ( one of the reasons the USA exists today) was a riot against the wealthy English class and it started the American Revolution.

The root cause of most rioting is usually class warfare, even though the catalyst that starts the rioting can be something unrelated to socioeconomic conditions, the extent of how bad the violence escalates depends on how badly the system has broken the poor class... it unfortunately usually ends badly for many people, but there are always many more poor people who have nothing to lose than there are wealthy people.

Many people seem to have forgotten or just don't know that the reason the USA exists today is because it was created with violence and rioting.