You can add a pro-con page on any topic for which it is relevant from the left sidebar on each page where you see "Add Pro-Con page".  Just click there and voila!  The pop-up "how to" box will show you how to add the "Pro-con" box to the right sidebar of the topic page to reference the associated new page you've built.  You can find an example of a pro-con page HERE (although it's just a baby, later it will have cool features and a brand new look, something like this):