The "we" stuff happens among every fan base I've ever witnessed. When it comes to sports, some people just can't grasp the difference between who's in a group and who's not. I don't know if it's because "we" was more accurate when mom and dad were helping coach junior, taking him to practices, and paying for all his equipment, and thereby making it a team effort, or just because the "we" people are that desperate to be a part of a group. And I've mistakenly typed "we" on occasion, since I've seen it so often, though I go back and fix it if I see the error.
It's not as if people are going around with the "we" stuff when they buy a car, television, computer, or the like. They're capable of realizing that liking Apple/Sony/Samsung/HP/etc... products doesn't mean they're a member of the company. They just lose that bit of common sense when it comes to sports. They erroneously transfer the "we" of the fan base (a/k/a repeat customers) to the "we" of the team.