This is one of the underlying issues with government as a whole. Since everyone pays for the roads why can people not do what they would like on property that they partially own? All these arbitrary laws and arbitrary rules are tough to follow, so on special occasions I see no harm in it.
Now, if you're going to celebrate, as long as you're not causing harm or destruction, not stealing or breaking into other peoples property, I'm okay with people celebrating and having a good time celebration. But, if the roads are not shut down, don't block my only way home. People do have places to go. Celebrate on the sidewalks or at the park.
Fans should never block traffic even if their team wins. Running into the middle of the street blocking traffic is dangerous and causes infuriating traffic congestion. The congestion caused by fans taking over the street will only make more people angry, which may lead to even more trouble for law enforcment and city workers along with the general public.
It's difficult to approach this topic without seeming xenophobic. The argument is simply an exercise in civic responsibility. Regardless of the reason, it is disrespectful to impose upon and disrupt the lives and behaviors of those in the city who do not share the fans' zealousness. Have forethought and make arrangements with the city to hold a possible celebration in an appropriate venue.
Regardless of what the occasion is, anti social behaviour is not acceptable. I see distrusting the flow of traffic as being anti social due to the fact that it disturbs the life of another person. I do not see why celebrations cannot be kept within approved buildings and areas, where it will not have a negative impact upon others.