Two thoughts.
Facebook is so pervasive these days, although like PeteS I refuse to use it, I suspect that the majority of people looking for fell running information or online interaction probably gravitate to facebook (or should that be meta) and don't even give the forums a second thought.
Another forum I frequent does not allow any political or religious discussion. Specifically to avoid any ugly arguments on those topics. General chat about anything else (unrelated to the main forum topic is no problem) flourishes. The no politics or religion is actively moderated with polite notices from the mods and threads locked where necessary. I think this rule is a real benefit to maintaining a (mostly) friendly and harmonious community there.