When there is any large gathering of people, the potential for chaos becomes very high. This is especially so when there is a division within this large group of people, say fans of different sports teams. Some people take spectating sports extremely seriously for reasons unknown, as they are not even players or related to them in any way shape or form.
Regardless, in any group situation where there is a chance of a brawl, it is highly important to not lose focus on the environment. Adrenaline rushes tend to give tunnel vision, and that is exactly what isn’t needed in a situation such as this, as the risk of getting blindsided and seriously injured is quite high.