Fear. Most people are afraid of weapons of any kind. It is a fact that there are people out there who will use violence to further their own ends. (whatever those ends may be) These people believe that simply disarming the violent individual will solve the problem. (Gun control anyone?) Now, if this works in their mind... No weapons = no violence... then is stands that weapons = violence. So if you are someone who carries a knife, or keeps a gun in your truck ect... then you must mean to do violence.
What these people fail to realize that it is the person behind the tool (I don't like the term weapon... my knives and guns are simply tools) that matters. If you intend to cause harm, you will... regardless of the 'tools' at your disposal.
Just my thoughts on the subject.
D