Habit formed over years of showing the 911 debunkers are morons.

Edit: people 2001-2004 would physically attack you potentially for suggesting false flag. 2004-2008 was a period of semi-rational discussion where many of the "investigations" were complete. It was possible to convince some during that period, but calling it a demolition set preprogrammed responses in people and so even to have a technical discussion would require using the term collapse.

If the barrage of downvotes is for not believing 911 was inside job, you've never read the NIST report. That debunks the official story better than snopes could do.