The Chinese average two mass knifing incidents in schools each year.
In most cases the attacker suffer from mental health problems. In China, like the US the breakdown of a family support structure is a contributing factor.
The breakdown of the family support structure points to the individual which for those who like to focus on the tool, that human root cause is too uncomfortable to bear.
The oft criticism is: If there is no gun, there would be no shootings.
Since the car is is often involved in crimes, do we ban the car? The car does not have to be used outside of its intended design, which is to transport things. Transportation and its various tools have been used for both good and evil purposes. The keyword here is 'purpose'. Inanimate objects do not have purpose. Humans do. Purpose have tasks which create the need for tools. So if the car is used to transport illegal drugs or bank robbers, banning the car would create problems for those who would use the car for good as well as evil. Look at it another way, if you do not like prostitution, do you ban sex?
Arguing that the gun have only one use -- killing -- also misses the point. Somewhere in the evolution of man, we developed the need to kill, from prey for food to other humans for conquest or self defense. Weapons, from the rock to the gun, were developed for that purpose: to kill. Self defense is a good act. Murder is an evil act. Banning weapons does not do away with immorality which make up those evil acts. If someone want to do you harm, he will find one way or another to create a weapon if there was none. Now you have to find your ways to one-up that person if you want to defend yourself.
So it still fall back to the true root cause: the individual.