But the size of the crowd in a sports stadium doesn't account for it.
Rugby International crowds can be of similar size, and just as biased in their opinions, but the same problems don't flare up.
Cardiff's Millennium Stadium was host to numerous 'Football' cup finals while Wembley was being redeveloped. There were no major disruptions. Admittedly the bars in the stadium were closed on those days, but there were lots of pubs on the way in (from the segregated fans parking at different points in the city).
The same crowd for a Rugby international will be sitting in the stadium with the supporter groups intermingled, and the bars open. - No Problems!

It must be down to the attitude of the sport, and its supporters.