On the question of how to let newbies know this section is an option:
Instead of stickies, y'all could use vBulletin's automated welcome PM to new members feature and stick a comment about it in there, if you'd like. They tend to get read more than the emails.
On the question of whether or not making this section opt-in, I'm agnostic. Whatever makes everyone happiest.
I might peek at those topics occasionally, but usually avoid them. Mostly because it's sometimes easier to be friends with people when you don't know all their political and religious views.