Unwavering Loyalty: The Sporting Fans' Ideal

"I still support the Cowboys despite their performance in the last six years."
"The Cardinals are your favorite team!?! Go die."
"You don't like Liverpool, you've never even been to a match."
"Well, I'm going to be honest and admit that I tend to follow whatever team is most likely to win."

The loyalty of fans to individual teams is an enormous part of sport, especially amongst the fans themselves. They brave decade-long droughts of poor performance, confident that their team's day will come again. They argue, riot, and even kill as they band together in large armies to harass an equally riled mass of fans on the other side of the pitch. A loyal fan is weary of accidentally embracing a false supporter, an impostor. After all, those who come quickly will leave in the same manner.
I propose the following evolution-based explanation for the intensity of the emotions that come with sport:
In today's world, it is difficult to make alliances that feel as though they are more than just agreements to spend and enjoy some time together on a regular basis. There is little need for making pacts with others to prevent your own death. We no longer have neighboring communities that lurk in the shadows, waiting to take our compound by nightfall, from whom we find protection only in our own numbers. There is no longer a need for strong bonds between hunters, the willingness to "work for each other" in order to survive on a day-to-day basis. When there were such needs, those who made they strongest alliances were usually the safest and best feed, hence the very strong desires that exist in modern humans, the descendants of those who survived to reproduce and nurture their offspring. So today, we look for other places to make these alliances. We look anywhere and everywhere, desperate to find a group. This desire is ingrained in us. The loyal fan is respected and trusted to support his favorite team. The supporters of other teams are hated, harassed, and avoided. Fans with seemingly weak or questionable ties to a team are watched carefully and not trusted fully. At the same time, fans may attempt to jump ship as their team sinks in defeat in hopes of making friends with another group of people in support of a better-faring team.
It's simple. It's evolution. It's all very exciting.