I’m not seeing how a pistol would help here. In most circumstances that I can think of, drawing a weapon against a shoplifter—to say nothing of using it—is more likely to result in charges against you than the thief. Unless you can prove you were in imminent danger—you tried to stop a thief and
they produced a weapon, say—I think a lot of juries are not going to look kindly on your decision to brandish a weapon in a crowded store or street. The risk of harm to bystanders is too high. (And a gun isn’t going to be any use against a thief who’s already gone, or apathetic cops who don’t give a damn.)
I don’t have any problem at all with people resorting to lethal force as a means of self defense, and if this was violent crime we were talking about, I’d probably see it differently. As far as shoplifting, I do believe that a community of armed, on-edge people looking for criminals is likely to be more of a threat to public safety than the criminals themselves. I think more effective surveillance and forceful prosecution—as well as whatever social measures can proactively reduce crime—is a better approach here.