Why do many people have pointless arguments?

Basically pointless arguments come from pointless people. Those with nothing better to do than stir up strife. It all boils down to the anonymous faceless person can say things, that the individual would never do or say in person. Public convention does not allow for the unimpeded voicing of opinion, where as the very anonymous nature of this forum breeds the kind of pointless arguing you mention, because there are no reprisals for such behaviour. In short human nature.