I don't know of any, but do they have to be message boards? You could try Yahoo! groups and other email lists. If you're looking for a professional discussion/debate, you might try finding websites on the topic and contacting the webmaster to see if s/he knows of any such boards. You might also look on Google for "message board" or "forum" or "board" and "database" or "directory" or "links" to see if you can find sites that list lots of them, then search on those sites.