Guns are tools. They are designed and built to do one thing. Guns themselves do not kill people. Yes, it is easier with a gun but that's what tools do...make things easier.
Hammers are designed and built to do one thing. I can kill someone with a hammer. That's not what it's desiged to do...
Gun makers shouldn't be held liable for crimes commited with their products. If that's true, we should hold the same reservations for knife makers, car makers, aircraft makers, tool makers, carpenters, grocery stores, etc...