I think politics and religion are very different than most other disagreements because they extend beyond that one person. When a person believes in fascisim or racism, they begin advocating policies to force their believes on others. Religion gets tossed in there because a long time ago morality got tied to religion.

So in my opinion, people get into "religious wars" because the beliefs of other affect them.

Hell, when people get all worked up about a language there are benefits to convincing people to use their language -- better tool support, better libraries etc; and if they are on the losing side of a language they will have to learn another one.

In the end these types of debates are all about control, either direct or indirect. Direct -- Force, rule of law, etc ... Indirect -- public opinion, social mores, # of followers.