Let's start with debunking the view that “football is stupid”. There is a Borges quote that says something like “football is popular because people are stupid”. Well, Borges said many brilliant things, but this is not one of them. I have been rereading “Gödel, Escher, Bach” (if you do not know what I am talking about, sorry, go look) and some of the characteristics of intelligence seem to be (this is copyright by David Hofstadter):
to respond to situations very flexibly;
to take advantage of fortuitous circumstances;
to make sense of ambiguous or contradictory messages;
to recognize the relative importance of different elements of a situation;
to find similarities between situations despite differences which may separate them;
to draw distinctions between situations despite similarities which may link them;
to synthetize new concepts by taking old concepts and putting them together in new ways;
to come up with ideas which are novel.
I defy you to find just one football situation where all of the above does not apply. In fact, once you have the ball, your brain is running on turbo mode. And since we are on quotes, let me remind you of Boulez saying somewhere that “music is the unpredictable becoming necessity” - and this applies to football, this is exactly what happens in every game, once the ball is in play. The ref whistles, the attacker passes the ball back, and after that, everything is unpredictable, and necessary, once it has happened. The central tries a pass to the right lateral, he tries to get it and somebody from the other team gets it, tries to pass, fails or make it, etc., etc., etc. It is a mirror of history, which works in not so different ways. Chaos and pattern, all together.
Also, this happens because football is a sport where actions are not repetitive enough to be easily condensed into statistics. I am not referring to those stupid commentators who insist on saying: “The statistics are against X winning, because Y has won three times out of the five they have played”. To be statistically significant, we would have to talk about thousands of times, not five. In tennis, or in basketball, things are much easier. In that sense, as our national philosopher, Óscar Tabárez, has said, “statistics are there to be broken”. Which means, football is exactly on the edge of the predictable and the unpredictable. As we all are. So we “root” (beautiful word) for a team, knowing that probabilities are against us, but... who knows? Maybe this time it can be different, and sometimes it does happen. The present World Cup is a perfect example; most of the favorites are gone. I write after the first semifinal, so I do not know who will win, but it does not affect the reasoning.
And one more point. It is just beautiful how national character (good and bad parts alike) ends up reflected somehow on how a team plays. In that sense, football is as good as food, or classical music, if you want to know how a nation's heart beats without going to the trouble of learning its language, history, literature. Watching the Russia-Croatia game you can understand 1812 or 1945 quite well. Never mind who won. Any game by Uruguay (allow me to be a bit chauvinistic here, I am just a fan) will tell you more about who we are than many books which you will not have the time or will to read.
Clubs are of course something else, but they have their own culture, and it can be beautiful, ugly or middling. The sense of belonging is important for us, we need to belong, and rooting for a team gives you an inmediate high of this. It is ok, as long as you remember that this is only for 90 minutes. And there is something very uplifiting about being one out of many, sometimes almost a mystical experience. It does not, and should not, mean that you think you are better than the others because your team managed to make that goal in extra time, you (should) know it is only for this game and only for those 90 (or 120) minutes. But, boy, it really feels great. Of all the meaningless things mankind does, football is one of those which has some meaning.
Which brings me to the last point. It is heaven-sent that we can be completely irrational for 90 minutes and (presumably) wake up afterwards and think, well, it was only a game, they played better, or we did, and go on with our lives. It is not “opium for the masses”. It is just football. Enjoy it. You can worry about social issues or whatever interests you during all the rest of your life.