Generally it is good natured banter, sometimes it gets much more than that. I still remember a bunch of English guys I was with on safari in Kenya years back, we found a shack with a TV to watch England vs Greece. There were a couple of Scots in there as well and they cheered loudly when Greece scored and we laughed along wryly, when we equalised a Scottish girl who was in our travelling group said we shouldn't cheer because the guys behind us wanted to hit us for it. Of course the roof went off when Beckham smashed in that equalizer, they never attacked us but we got all the evil stares you can imagine. But it got to that point, that we could not cheer our own country scoring a goal in football? That's not banter, that's bordering on racism driven violence. In other words, utter bell ends.
Is that not a football thing though ? I don't know the first thing about football as to me it's the most boring game in the world but it does seem to bring out the worst in people.