What I want to suggest I don't know if it can be possibly practiced but i know that if it's being practiced, it can stop the repeatedly fighting and what I want to suggest is that the stadium should have a barricade to seperate both fans from sitting next to each others. The stadium should be divided into two parts and let the fans of each team occupy their seperate parts and should not be allowed to go to the sits of the fan of another team. If fans of the different teams can be kept separately, it would stop the fight, maybe after the match they can fight outside the stadium.