I personally can not see any thread in any area on political topics lasting long at all. People have varying and different opinions and that is a good thing but all threads will head south very quickly...opt in or not. It really would be a full time job to moderate.
Would it be worth it? In my opinion no. Some members can and do carry grudges over comments made to their car related posts...Imagine how much angst it would cause!
Great idea in principle, but it practise, I just don't think it would be good for the forums.
Just my little $2.20 on it. (see, even added my GST)
Cheers
Col