Music is a very personal experience and what you get is a bunch of people gathering to experience it live. Very seldom do you get fandoms of separate artists who have a combative relationship.
Sports are communal. The teams are named after cities, states, regions, or school districts; and they typically have nicknames that represent the people or the area in some way. They are seen an extension of the community or region, not merely entertainment but something a step above.
You assume everyone cares about sports. I have a number of friends and cousins that are musically inclined and don't give a rats ass about sports, but feel very connected to certain musical artists/groups and defend them with a rabid fervor.
My cousin almost lost his shit when I said Hendrix was a better gutiarist than Stevie Ray Vaughn.
It's about people's passions and some feel connected to teams/artists/actors etc and others like myself just care about the entertainment value.
You have a favorite team, ergo you identify with them on some level. You chose them over all of the other possible teams. Taking what you say at face value, you're obviously less invested than most people and that's fine, but it's certainly no more normal or rational than someone who feels more invested in the fortunes of said team. It's just a choice that you made.
I don't understand what you mean by, "I was always me". You understand that you don't lose your individuality when you identify with a group, right? If you were to say "we're getting coffee", with the "we're" referring to a group of friends, you're still an individual as well. Any association that humans form exists on a spectrum. There probably are football fans who feel as if they're actually part of the team and have an unhealthy emotional dependency (something like Big Fan). There are also football fans who just want to see the sport be played well and don't really care about the outcome. Then there's you and me and everyone else that falls somewhere between those two extremes. No one degree between said extremes is inherently the right one so this whole discussion is really peculiar to me.
I think that if you (in the general sense, not you specifically) genuinely care about something as insignificant as someone's pronoun usage, you're pitiable.
I'm just me, nothing more. I don't take accomplishments others have and pretend I'm part of it. If I love a movie by a director I like or a song from my favorite group, I'm not going to refer to it as "our movie" or "our song"... I had nothing to do with it, I was simply entertained by the art and supported the artist by paying for the movie/CD. That's my part in it, nothing more.
With the Pens or Steelers, I don't identify with them or place my self-esteem in how they do. I want them to win, but it's not life or death for me.
I'm passionate about hockey and love talking about it, well beyond the Pens. I'm just not connected to the Pens on a personal level where I feel like a part of the team.
It's just how I'm wired and always was.
I just want the Pens/Steelers/Social D etc to entertain me, nothing more. I don't care about meeting any of them or their personal lives. I don't feel a connection to people I don't know. Just because I see them on TV doesn't mean we have a real connection beyond them being entertainers.
And once again, I don't care about other people's business and if they want to pretend to be a part of a team they don't play for. My point was for the third time, it's just funny how so many people conveniently switch their pronouns based on how well their team is doing, from "we" to "they".