But seriously, how much of this is just thinking fast on your feet? Common sense? And not a small amount of luck...because ISTM that if the bad guy you're trying this on is wired up on meth or crack, his reasoning skills are going to be less than if it is just some guy robbing a bank stone cold sober.
There is definitely some common sense and fast thinking involved, but training can help a lot. You can frequently verbally de-escalate even an acutely psychotic person if you know how. I spent most of last night doing it, as a matter of fact (I work on a Mental Health unit). Does it work 100% of the time? No. But then again, neither does anything else. Having an extra tool in the toolbox is never a bad idea.