I don't understand, at all, why it's considered "douchey" to wear apparel that promotes your favorite team, even when they aren't playing.
Yes, I will admit, there are some strange occurrences, like that guy in Kansas City, who sat right behind home plate during every game of the World Series, donning a Florida Marlins cap. To me, that was a bit over the top, because he was sitting there every single game, and was in a great seat.
On the other hand, I got a kick out of the kid about 5 years ago, who wore a UK hat at Cameron Indoor, and he was sitting right beneath one of the baskets. Again, if he was a season ticket holder, and did that, it would be weird. But one game? Go for it.
I also actually think it's appropriate to wear your team's apparel when you attend a game where the results can impact your team. Now admittedly, this is "classier" if, say, you benefit from the home team winning, as opposed to the road team. There is no reason to pick a fight, after-all.
But in this instance. Two teams out west. Then, who cares? Go, big blue!