All about proportionality, big differences in nature of tackles and big differences in pitch invasions. Fan runs on is automatically committing an offence and risks a ban but good natured celebration of a goal is a world away from kicking off. If the fan tried to take a selfie the goalkeeper may have over- reacted. Self-defence, in law,isn't a right you can award yourself. It has to be reasonable. If someone went up to a copper at a match, or New Years Eve and went to take a good natured selfie he can't just be thrown to the ground, that would be assault. Footballers don't have a different law to the rest of us. City equalised, some fans overdid the celebrations,it happens. There really are some po-faced holier than thou twats on this site sometimes.