A tool to defend is a shield. A bulletproof vest is a tool for defense. A tool that is meant to penetrate a human body is not for defense but for offence.

Unless you mean just showing the gun without bullets. As soon as the gun carries live bullets then it becomes a offensive tool rather than defensive tool.

That is really just another way to bend the truth by calling guns a defensive tool. Go back to the time of bow and arrows which are probably a hundredth less powerful than a gun as far as loading time and number of shots fired. Would you say bow and arrow is also a defensive tool?