I like the police analogy. When most people think of someone carrying a gun, they think of some low-life drunken scum, not the police, and certainly not a room full of people at a PTA meeting, but it can be all of those things.
I like taking people down that path by getting them to think where they'd feel safest if someone were trying to kill them. If given a choice between a high school where guns aren't allowed, or a police station, they usually choose the police station. I won't go into detail, but you can see how you can quickly make them see that the reason that they feel safe in a police station is that if worse came to worse, the police can shoot the neanderthal who is trying to kill them. Therefore the place that they feel safest is a place full of young men with lots of guns.
Unfortunately, some people can't get beyond the "yea, but they're police" thing, as if the police are some angelic entity, and everyone else, if given a gun, would shoot the person to their left.
There's a good come-back to several issues on this site:
http://www.shotgunnews.com/members/fred/pages/Freds8.html
His response to this one is as follows:
WE SHOULD SAY: "Your claim that
'they're only for killing people' is
imprecise. A gas chamber or electric
chair is designed for killing people, and
these devices obviously serve different
functions than guns. To be precise, a
high capacity military-type rifle or
handgun is designed for CONFLICT.
When I need to protect myself and my
freedom, I want the most reliable, most
durable, highest capacity weapon
possible. The only thing hunting and
target shooting have to do with freedom
is that they're good practice."