Sounds like the consensus is that if a thread/topic gets heated and looks like it may combust we just let it do what it naturally will do out in the open in the thread.
Ummmm.........not quite. If a thread is getting ready to combust, what will typically happen is either someone in that thread will ask for calming heads to prevail or the mods will step in. Or.............reporting a thread to a mod to let them know that this really good thread is getting out of hand and that they may want to come in to raise some caution flags.
Just letting a great thread combust and eventually get shut down, in my opinion, is totally unproductive. Not only that, if one puts a lot of thought and time in participating in a debate, it's pretty upsetting to have it shut down. I know. I've been there.
But taking a good debate and a good topic to PM's deprives the rest of the community of, what could be, some great insight into certain topics.