[quote name='fullmetalfan720']Do you think someone would pull a gun on someone if many people around him had a gun?
Would you steal someone's stuff if they had a gun at their waist?
Why would anyone pull a gun on someone if they knew they would get shot by doing so?[/QUOTE]
Well like dmaul has said, someone pulling a gun on somebody else isn't always rational and it happens all the time between criminals, etc. Hell, people shoot at cops.
Plus, a gun doesn't put up a bullet shield or something, you have to have the chance to pull out the gun and fire it, if someone already has a gun on you, that's not a very good idea, as you will probably be shot.
I agree that there's logic in what you're saying: If you think the other person might have a gun you won't be as likely to pull a gun on them, but there's also logic in shooting someone first so that they don't have a chance to pull their gun on you, so the gun isn't an automatic defense just by virtue of its existence.
I just don't think that the logic applies in as many situations as you think. People don't normally have a gun pulled on them (to be robbed, etc.) in the middle of a group of other people, so the number of other people who have guns is irrelevant in most situations. And the heat-of-the-moment shit we're talking about with stupid kids is exactly the situation where the person wouldn't really be considering whether or not anyone around them had a gun before they pulled the trigger.