In case you haven't noticed there's a lot more than politics discussed on FR. Football isn't a political topic, yet I seem to recall seeing a few threads about it.
I understand that, and Narnia has been discussed along with other secondary topics. You asked why Brokeback was getting so much attention here, that's the reason. It's a film with a political agenda. And this is a (primarily) political board.
I'm not entirely sure why you're splitting hairs here. The answer to your question is fairly obvious.