I've used this anecdote a couple of times, but I once sat behind someone who slagged David Silva off for the whole game and sarcastically applauded when he was subbed off. He didn't have a bad game, just hated David Silva, of all people. We won the game, he was involved in one of our goals.
There are some City fans, and I suspect some football fans, who don't know how to engage with their team outside of negativity and hostility. Plenty on here. That isn't to say we should never be critical, but there are some that don't know how to support team outside of being absolute bell ends. Dunno if the 90s broke their brains or whatever.