I think it is a combination of two things:
First, once you remove traditional morality and self control, you have to worry about all the untamed animals that are produced. Each child is an untamed animal that has to be trained to be a responsible member of society. Remove and denigrate that moral training, and you have a lot of dangerous animals being produced.
Second, the carry and use of knives in traditional roles require and promote the idea of independence and responsibility. Both are anathema to collectivist thought. Thus, the suppression of the carry of knives helps to promote the themes of dependence and reduced individual responsibility.
Does this mean my 13-year-old granddaughter, who killed two deer this year with her .308 Savage, is an ‘untamed animal’? She looks so sweet....