Being a fan of a sport is a fucked up version of tribalism. We used to just kill people that weren't part of our tribe (family, friends, or a greater sense of local community). When nationalism replaced tribalism, people redirected tribalistic attitudes towards less meaningful things, like competing in sports. In schools, this makes sense: you're supporting your own classmates playing against other schools. In the past, professional sports made a little sense: you were supporting athletes from your community, men you could actually know, and their team represented your community. As we all know, the growth of multicultural cities, the collapse of a sense of community, and the jewish profit-seeking methods of professional sports leagues, have created a situation where there is no longer a coherent tribe and, even if there was, sports teams don't actually represent their supposed home anyway.