What it comes down to is a simple concept called being proactive. Most mods have been members here for years, some of us have been mods for years. After a while you get to know what sort of threads are going to degenerate into slanging matches. Then you can go 2 ways you can nip it in at the bud before the crap hits the fan or you can wait for the inevitable then clean up all the crap. What do you reckon is easiest?
Does it make that much difference in a general members life if a provocative conversational thread gets closed? I doubt it, and if it does perhaps that member needs to get a life. But leave these threads to turn to crap and it makes a difference in the life of the admin/mods who have to clean the crap, we all have jobs and a lot of us have families and partners and every minute we spend cleaning this crap is time we could spend doing something more worthwhile.
So now do you get the idea why some of us would rather spend the couple of seconds being proactive, clicking on close thread rather than half an hour being reactive to the crap?