The mind is humanity's most lethal weapon. With the "right" mindset the entire universe can become a weapon. Efforts to reduce violence tend to focus on the presence of concrete weapons (because this is easier to quantify and measure etc) with much less focus on violent ideation and the root causes of the various forms of interpersonal violence.

Reducing violence is a tricky thing because to a large extent it seems to me to be a symptom of broader and nearly intractable societal malaise. Not that it isn't worth removing nuclear weapons from circulation but the returns diminish quicker than most public policy folks seem to want to admit.