As a Pacifist, I say protesting is fine as long as it doesn't turn violent. Rioting doesn't do any good and it helps a cause worsen than get better imo.
sometimes, very rarely, it is because people feel like their voice is unheard, but most of the time, some guys got drunk and other people decided to join in
Because they are dumb people. People who were not born with the gifts needed to obtain the things they want, at least in today's societies. They have a huge sense of entitlement and know that the only way they can have the things they want is to riot and loot to get them directly, or "protest" to change policy so that lazy losers are given money for doing absolutely nothing. These are facts.