There is no excuse for attacks on the police. Anyone caught, arrested and convicted should face the stiffest of penalties.
But banning the Carnival? I don't think that is a proportionate response. If we ban the carnival, then we need to shut down every single pub, bar and nightclub that the police are called out to in every urban, suburban and provincial town during kicking out time.
...because the police face assault and injury in these environments 52 weeks of the year.