Having reacted to violent threats against others before,
I can honestly say I don't know what I would do. It is always situational for me. I do care what happens to other people and I will engage; I know, not just `cause I'm saying it, but because I've done it . . . at least twice. Neither time involved the use of a weapon, though once the potential existed to escalate to that level (the other time, I was unarmed).
The scenario being discussed here is just too vague to know what to do for sure.
Do I think . . .
. . . citizens should stand up for and help one another? YES
. . . I should always draw my weapon at the first sign of trouble? NO!
Again, too many variables in this described scenario. Bottom line is that most people will never be trained up enough to handle every situation perfectly. We should just hope to God we are good enough and wise enough to do what needs to be done at the proper time.