It's really just fanboyism. People developing an obsessive loyalty to a product they buy to the exclusion of all others. It often occurs in gaming circle because usually a single person can afford only one gaming system, so they will argue to the point of obsession to prove that theirs is "better" and that they made the "correct" choice, while everyone who disagrees made the "wrong" one.
It's pointless and pretty annoying, but it's been going on for over since the beginnings of the industry, and it's not going to stop anytime soon. The best thing to do is just ignore them, kids can get like that, as can adults really.