Well, opposing viewpoints frequently meet in wikis.  "Neutral" POV and "common sense" are highly subjective and the only solutions are to either favour one viewpoint as a matter of site policy or to let people battle it out.  If you choose the former approach, admins need to monitor contributions very carefully.  If the number of contributors is large, you have to police the site through very "blunt" use of editing restrictions (massive IP range blocks, night editing restrictions etc) which slows the development of the wiki considerably.  If you choose the latter, editors are allowed to run free and the project grows quickly.  However, you can end up with long, protracted debates between editors about seemingly trivial points.

Wikipedia was founded on the principle of allowing very open editing with minimal intervention by admins, and I doubt that will ever change.  You can console yourself with the fact that all of the millions of articles here can be copied freely (under the terms of the Creative Commons Attribution ShareAlike license) to other wiki projects and edited to suit the viewpoint of the site!