Being designed to kill is irrelevant as it is neutral. Being designed to kill is subjective because it is neither good or bad. If you are hunting then being designed to kill is good. If you are going to defend yourself from murder, rape, robbery, then being designed to kill is a good thing. Designation doesn't mean anything, it is a tool, and like other tools it can be used for good or bad. The most recent mass casualty attack involving a terrorist involved a truck, not a gun or a knife. What matters for a tool is what someone does with it.