I posted a response here more for open discussion and future reference. It would suck to have to revisit the same topics later.
Sorry if it made you feel uncomfortable.
Although I try to avoid political and religious discussions as much as possible...well..they simply will happen on forums; and, as you said, if you don't have a place for them, they will take their place elsewhere.
Though my forum doesn't get much activity, I initially started the forum with a special section called 'The Outhouse', which is the crap receptacle; anything posted there will not be listed in new posts, to try to keep it from spilling out into the rest of the forum.
I am the complete opposite of mods and admins who like to lock threads and delete posts: it would have to be one extreme situation for me to even consider locking a thread or removing it (outside of someone spamming the board). The only restrictions I have imposed is to have an adult section and a rants section for such conversations, of which neither will show in recent posts.
There is some value in allowing the boys to crawl the P&R section. First, there's plenty of traffic. I see P&R threads from DP in the SERPS all the time. Some of the people that open the threads may even be webmasters and join the forum. Second, the users that post in the P&R can get a little traffic to the signature.
I marked whole General forums to not show in my Unread posts count, yet as a moderator I should not do that. However there are too many threads there that eat my time and I cant afford that to myselft.
religion forums section is like having a warzone, so expect the flames :D