Guns are a special kind of object that shoot bullets. Bullets are pieces of metal that move very fast and put holes in things, animals, and people. People use guns to do any number of horrible things, all of which fall under the category of violence. Sometimes this is just psychological, but a lot of the time, it is physical.
As if that wasn't enough danger for one horrible object, people are often careless with their guns. Every year, hundreds of people are injured or killed by guns purely by accident. In addition, especially in America, far more people are allowed to have guns than a reasonable person would expect. This prevalence leads to many other problems, like mass shootings and school shootings, that generally don't occur in other places.
Even the people who are "supposed to have guns" are not safe people to have them. A notable example is the cops, who semiregularly shoot people for little or no reason, sometimes including each other. If they did not have guns, they would not be able to shoot anyone, which sounds like a big improvement.
Guns also make wars worse. After guns became prominent in warfare, more people died every time there was a conflict. In other words, they even make war (one of the most dangerous things) even more dangerous.
Lastly, guns contribute to negative outcomes for people who are exposed to them all the time. They are very scary, and being surrounded by them likely signals that you are in an unsafe situation, which may have lasting consequences even if the guns are not used.
Guns are designed exclusively to be dangerous. That is the entire point. We took 0.1 point off because they technically don't do anything unless wielded, but we still consider guns to be just totally dangerous and frankly an awful misstep on society's part.
