Why we take sides?

Well we all have a habit of supporting one team over another. In election voting in favor of one party and developing dislike for another. Sometimes we have solid reasons for our support but most of the times we are just biased.we Like one and hate another. Pray for one like he is your brother or sister and want other to lose badly like he has murdered you three or four times.No reason but you just feel it .We support the best players of the world and give reasons for their support such as their brilliance and class .Football  fans are ready for war to support their teams and losing is not an option. But if we support the best then why we choose a random guy of ordinary capability and skill and get behind him. He who is not even fit to play at international level gets our support. Strange na. We actually don't have a behavior pattern when it comes to supporting people. We like someone and hate a stranger  just because we feel it.Even best of scientific research cannot figure it out and yes they have tried only to end up with stupid theories which they can't explain themselves. Actually when it comes to supporting the best it is his skill which mesmerizes us and when we like a loser and want him to win is that we start finding our reflection in him. Just pick a random guy and get behind him because you feel a connection and he will represent you on platform where you can't reach. Ok that seems to be a fine explanation. But what when we are against someone. What we want one to lose badly. He hasn't done anything wrong. But he must lose. why? because we hate him. We envy him and he is like the guy who you couldn't beat in any of those stupid encounters you had in your school or college.