Fans buy tickets with their money, they can stay or leave whenever they want. Had I been at the game, I would have left early. I would have been extremely pissed off about the game, and if someone along my way out decided to "boo" me, in the mood I would have been in that person would have ended up with a few "boo boo's"
Let fans do what they want and shut the fuck up and watch the game if you want. If people are not doing something violent/destructive/disruptive or anything otherwise illegal, who gives a fuck if they want to leave early.
I value my time. Once I feel the remainder of a match is not worth my time, I leave. I'm not going to sit and watch my team play like shit, already down 5, 6, 7 goals just because "you don't leave early". Fuck that that and fuck you.
I'll almost never leave a 1 goal match early unless something personal comes up.