Why "Guns Save Lives" (GSL) you ask? It is really quite simple and there are several valid reasons.
First, "guns in the hands of responsible law-abiding citizens who're willing to accept responsibility for defense of self and others" doesn't fit very well on a button or sticker!
A need was perceived to find a catchy slogan based on certain accepted facts. Through some transition of style, the present form evolved and more importantly it works.
GUNS SAVE LIVES has a high recognition factor and promotes the positive. Response to the slogan, even from the antis, contributes to expanding the influence of RKBA groups and individuals. That is what good PR productions should do.
Bottom line - GSL is arguably the single best pro self defense slogan to have been produced - and it started here in Virginia from a VCDL member's efforts a number of years ago. I would not change a thing.
BTW - At a recent past Lobby Day, some of us wore both the orange GSL sticker and the anti's People Save Lives sticker at the same time - IMO one complimented the other + it soured the expressions of the Brady Bunch to see their effort turned around on them.