I would contend that human nature is more complex than this. Take, for example, how people will respond to each other in a relationship (or an attempt at one). Most people are good - but we are living within what is an animal. We fully experience everything that animal would, normally, and have to process (or… Just act on instinct) our instincts against our ethics. Going on a sting of indulgent one-night stands after a break up that went ungracefully, for example, is both a natural reaction and a destructive one.
So is damning the engineer of a machine, that is difficult to work with, to the lowest tier of hell and promising to have him assemble cars with chopsticks coated in glycol for all eternity, while wishing you could thermite bomb the fucking thing through the concrete in a crater that would become a portal to the hell you will use to reign over people who make retarded designs.
See what I mean?
We have developed the institutions of society, customs, ethics, religions, and laws to provide ourselves and others with tools and consequences for managing the impulses of that animal component.
And not just the animal component. Just because I have good intentions and plans for a person doesn't really mean I can simply impose that plan on them. The divine component of humans can be just as troublesome, though not as obvious, as the animal component. We can't all be each others' god, and yet we are naturally inclined to assume this posture more so than many people realize.
Which is what it is - we have institutions for trying to assist in managing and codifying ourselves to achieve a more ideal state of living that provides as much freedom as possible while preventing the harm we can cause.
Most people are good and want to live in a good way - but it is naive to believe the raw, unrefined and undisciplined human is a force of good. While, obviously, our civilization arose from our nature - that includes our angels and our demons.