People are animals that have two legs and a big brain. They are you and me. They have a whole lot of ideas and do any number of things, including art, war, and websites. Are they dangerous? Sure, in some cases. But most of the time they are benign.
Whether or not you consider people dangerous is probably a function of whether you are considering people as a whole or as individuals. Most invididuals are not inclined toward violence and don't particularly want to do anything aside from guarantee their own future and security, i.e. maintain their ability to eat and stay dry.
On the other hand, people as a group are frequently given to bad ideas. Even if they as individuals don't wish ill on other people, they may still be complicit in creating that ill. Some good examples of this phenomenon are masculinity and racism.
If you encounter a person, you probably don't really have to do anything aside from maybe say hi. Nevertheless you should be aware that some people, especially the farther you go from home, will not necessarily be super friendly to you. It is generally impossible to know if someone will be friendly or not without an interaction, so the minimum amount of danger you can create in a situation involving a person is to pretend you don't see them at all.
People are responsible for many things, wonderful (like books) and terrible (like Facebook alike. There are lots of people—maybe 7.7 billion of them??—and they are generally all a little different from the others. Because of the variety, and because world history is rife with both acute and generalized examples of unnecessary hardships created by people for both other people and themselves, we have to consider people pretty dangerous.
