No, you pull your weapon if you feel you or someone you wish to protect is threatened with grievous bodily harm. You don't have to use it, though. Command voice interactions can cause the BG to desist.
Exactly. Pull your weapon if you feel you must, but if the guy says. "HOLY SH..!" and runs the other way at the sight of a gun, do you still shoot? Certainly not. I'm quite sure something along this line happens far more often than defensive shootings.