Metaphors carry layers of meaning. They're meant to connect two images or ideas in the mind of the hearer. The connection isn't just an intellectual one; without emotional undertones, it doesn't resonate. When Ronald Reagan talked of "morning in America," he meant that great days of possibility were ahead, but he also wanted to implant in his listeners an emotional sense of the beauty of dawn and wide open spaces.
Sarah Palin didn't literally mean that people should go gunning for Democratic candidates, not when she authorized a map with rifle crosshairs on "targeted" districts and not even when she said "Don't retreat. . . RELOAD!" (Although I admit it's hard to figure out what "Reload!" is a metaphor for. Fill up your fountain pens to write another letter to Congress? Think of a new witty rejoinder to someone's argument? Make a political donation?) No, what I believe she wanted was to associate herself with gun rights and gun culture and to connect herself with an ideal of the American Revolution - images of Minutemen and an emotional identification with ideals of self-determination and courage. She wanted to make regular old disgruntled people who were worried about money feel patriotic and heroic.
But metaphors have meaning, and they set a tone. Gun metaphors create a different atmosphere than, say, sports metaphors. What if instead of setting gun sights on certain districts, you said, "Okay, guys, these are the toughest teams between us and the Super Bowl. We gotta go in there and bring our best game, use our best strategy and play by the rules and beat them fair and square and humiliate them right on their home turf!" It's a klutzy metaphor, but you could still stir up enthusiasm, and it might be a bit more good-natured enthusiasm. It probably wouldn't be attractive to crazy people, and that would be a good thing.
Or what if instead of "Reload!" you found another catchy phrase. "When it's fourth and ten . . . go for it!" "When there's a wall in your way, jump over it!" "When they knock you down, get up punching!" (Hey, at least there are no guns in it.) "Don't shut up . . . speak up!"
Okay, maybe these aren't as punchy as the original. But I just spent thirty seconds on them. Politicians have speechwriters with lots of time. I'm sure they can come up with something catchy that has lots of positive associations in listeners' minds but can't be interpreted by anyone as advocating assassination.
Those who use violent metaphors want to have it both ways. When Barack Obama says, "If they bring a knife to the fight, we bring a gun," he wants to arouse in his listeners a sense of outrage and determination, but if one of his followers brings a gun to a rally (though it was always the other way around), he wants to be able to say that of course he didn't mean it literally.
Jared Lee Loughner didn't retreat. He tried to reload, but luckily he was wrestled to the ground by brave bystanders before he managed to do so. And it turns out Sarah Palin's metaphor was a little out of date. With a semi-automatic Glock and a clip of thirty bullets, you don't really have to reload: you can shoot nineteen people on your first clip just fine.