I'm always quite amused by things that wind people up at football matches. The leaving early thing always puzzled me although I do realise that for some people there is a good reason. When I had a Main Stand ticket back in the 80s there was an Indian doctor that sat a couple of rows behind me that usually left early. Apparently, his shift started at 5:30 so he needed to get away in time for that. I always used to stay back for 15 minutes to hear the final results which also meant I missed the worse of the crowds.
Half-and-half scarves was one that bemused me as I can recall Liverpool-Celtic/Rangers half-and-halfs back in the 80s and I also remember Liverpool-Everton ones being sold at the 1986 cup final. To me these were just keepsakes for special occasions and I have a couple: A Scotland-Germany one (which was given as a present from a German friend) and a Spain-Japan one from the Olympics. I think the outrage comes from people wearing them at ordinary league games as they are presumably bought by football tourists taking up seats from "real" fans.
I can't understand watching football, concerts or any other live event through the medium of poorly recorded smartphone footage. Particularly when so many games are professionally televised as well. I did used to do odd bits of photography at games but it was usually during lulls in the action. In fact, this was one of mine. It isn't the best quality as the photo it was scanned from is rather faded but can you gusess what goal this was?