its a silly phrase meant to imply that guns arent dangerous weapons at all.
When we know they are thats why they need to be handled with care or restricted.
Its kind like saying weedkiller doesnt kill weeds, people do. Or poison isnt poisonous.
It's a phrase that is probably used in a somewhat dismissive way at times, but It's a valid point if you don't try to read into it to much.
Guns are dangerous weapons. So is scripture if it is used wrongly. I would argue that bad theology and wicked teachings are far more dangerous to peoples lives now and throughout history than any other weapon.
The issue of gun ownership though is simple. You are commanded as a husband to protect your family, your church, and to some extent your nation. Guns are one of many tools available to assist in that endeavor.
Guns should probably have some restrictions. Unfortunately a lot of folks who want more restrictions don't realize the value of what they have.
EDIT:
The phrase is a valid point, because ultimately the problem isn't the tool itself but the user. Getting rid of guns may provide some relief, but you still have the underlying problem that isn't dealt with.
The biggest problem we have with guns in America at least is a cultural problem and possibly an economic one. Both of these however are trumped by the spiritual problem.