Mr.Squishy said:
[The] only thing I don't get is people who religiously watch sports on TV
This is something you cannot really explain to someone who doesn't feel the same way, which can be frustrating for both sides. For some people (like myself), a sports team can matter so much, each success and defeat feels like it belongs to you rather than a group of people you watch on tv, and to others who don't see this it's very difficult to come to terms with. The only thing you can do is to accept that some people behave like this, and to them it seems perfectly rational.
The difference between this kind of enthusiasm and the fanaticism that produces fighting and violence (because there is a difference) usually boils down to tolerance and rationality. Most people I know who are also sports fans are very accepting of other rival fans - one of my best friends is from a rival rugby - but if people become very intolerant and hostile towards other fans, instead of being able to accept that you have and are entitled to different views, then it gets nasty.