A weapon is as likely to escalate violence as it is to deter it. Taking up a weapon signals to your opponent that you are prepared to use it. A stick or metal bar can be used to disarm or incapacitate by striking the joints and muscles of the hands, arms, and legs without causing permanent harm. A knife can only be used to maim or kill.
Holding a knife signals your intent to maim or kill. If you pick up a knife you must be prepared to stick it into the body of another human being. If you are not prepared to do this don't pick the knife up, because it will be taken from you and used against you.
TOM M BAYLEY