I find it incredibly insulting to close a thread just because the people debating a topic are heated and passionate about their opinions. I know I've been involved in some of the debates that have been closed, but even though I am arguing a point against someone else's point and we have become a bit heated, we don't carry that on to other threads and are actually very civil and friendly elsewhere.
Another member and myself argued very passionately with one another on a topic, but are still good friends and happily chat about bullshit all the time, but because our opinions differed on a thread and we both became passionate about it, that thread was closed, insulting the both of us.
It's like saying "everyone has to agree or simply state your opinion and move on or you aren't allowed to talk about it" when you close threads simply because people are passionately disagreeing. Adults argue their points, that is normal adult behavior and is in no way unhealthy, so the moderation of these arguments and then re-posting the rules is in fact very condescending. Treating members like children makes them not want to post on any thread involving opinions worthy of social debate.