Okay, this mentality is really illogical and doesn't have a basis in reality, and here's why. The United States, despite its flaws, has never shown the willingness to cause as much harm as these smaller nations. The US has gone to war with other nations, but it's never tried to systematically kill them based on genetics and a pseudo-religious belief system, or a full on religious belief system. The United States has also not engaged in genocidal tendencies, ethnic cleansing, military annexations, nor authoritarian control of the state and people for a good number of decades now, the same decades as most of the western world. The United States has also possessed a powerful military as well as a nuclear arsenal, but we haven't used them to enslave our neighbors nor to reign death on entire countries to wipe them from the face of the earth. Even as bad as Vietnam got, the response to it was viscous and the government backed down to it's own domestic and abroad pressure, rather then say just setting off nuclear bombs in a scorched earth tactic.
Now, can you really make the same claim for North Korea? The same country, mind you, who still practices slavery?
Now, beyond the mere superficial of you comparing apples to a hornets nest for why having a bunch of one is good and a bunch of the other is bad, let's break down the crux of your argument.
People shouldn't have superior force to enforce peace, and doing so makes you a psychopath. Okay, then answer me this? Do you know how law enforcement works? Because that's exactly how law enforcement works.
The state empowers an organization, usually the police, with the ability to use things such as deadly force, and outlaws the use of deadly force for everyone else to use. They also then empower the same organization, or a different organization, with the ability to determine how the law is used, and whether to preform acts such as detaining someone against their will, which would be illegal for anyone not part of this organization to do. The way this system is enforced is via the threat of force, or the implied use of force when force is used against the state's say so.
Why is it that you think police officers are given guns as part of their equipment? Why do you think judges can sentence people to things, even death, without going to jail themselves for murder? The state decides what organization gets to do things, and which organizations or individuals do not, and this is enforced by the state having the ability to use deadly force.
According to your own logic, these individuals would be psychopathic for believing that they need to use violence and an arsenal to enforce the law. That they should focus on reducing their arsenals to get rid of their guns because everyone else doesn't get to have guns. And that any police officer with a gun is as big a threat as say a gang member wielding a gun.
In a way the United States is the closet thing to a police force the world has ever had, certainly more so then the UN which has watched millions die in cold blood and decided to do nothing about it routinely.
So the reason the US increasing its military is defense while NK raising its military is a sign of hostility? Because the US is like the police officer, and NK is like the crazy racist raving about having an assault rifle, threatening to hold their neighbor hostage if they don't get their demands.
I think if you had a front row seat for NK's wrath, you'd be hoping the police officer had a gun, and didn't simply have a book of encouraging phrases and reprimands to issue out for NK to sign.