If people question if we are having fun betting against our favorite team. Well for me its fine since as long as no money has been wasted and I win then that's important since we don't gain anything if we choose to be fanatic even if we are losing.
You are right, being a fan to the favorite team doesn't even give any benefit, the only benefit is when you bet on them or against them to win some profit from the amount you stake and you can only bet on them when you are sure that theirs a high chance that they are going to win the team they are playing against. For me, the fun is that I know everything about the team, their players, their performance, their past records and I can defend or support them if am in the midst of people arguing about sports and teams. It fun to join the discussion, knowing everything to narrate about your favorite team. But that does not mean I will bet on them to lose my money.