Why not just create a Politics and Religion category that separates those threads from the rest of the categories, better yet if you can set it up so that section doesnt a propagate the all discussions page.
This way, those who are so inclined can start threads and post in them and those who are not don't have to see them. These topics are not always apparent from the thread title and sometimes the content of a "normal" discussion can take a tangent so could be moved.
I don't think it needs to be a special permission Access like it was at the old FGI, you go in and visit and read and post if you want. If you don't , the content is out of the way .
I agree with Landon that there are a few folks who can derail a good site quickly if not kept in check . These subjects tend to deteriorate quickly and the known culprits turn to personal insults when they have no other intelligent recourse. Eliminate such discussions is the easiest way to avoid the problem but in the least, have a separate and isolated playpen for those who enjoy those discussions.