A more fair example, get bullied for much of your life, and you'll learn to fear other humans more than your worst nightmares.
People do have an infinite capacity for cruelty, but most people do not go there. Social dynamics are weird. I was bullied for a long time and had zero friends through much of my childhood as well. I've pretty well gotten over it. It's sure as hell had an effect on my worldview, but not on my appraisal of humanity in general. There are just certain situations where people get singled out for cruelty, and it's very rarely more than a small group of individuals who instigate it. Everyone else becomes passive participant for various reasons. They don't want to single themselves out in opposition to the group activity and just end up in your place. They don't understand what it's like to be in your place, and it doesn't sink in until much later that they should have opposed. They think that being forced to stick up for yourself will make you stronger, and they're actually helping you by not stepping in. There's lots of reasons these things happen, and they're all very fucked up reasons... but it doesn't mean that people are bad. Just flawed. Mainly our social structures are flawed and produce a flawed culture where damaged people spread their damage to others, and non-damaged people don't understand.
I used to think that everyone in the fucked up small town where I grew up was against me... and they were, in a sense... but it wasn't that everyone was actively against me. The social dynamics were against me. I was the odd one out in their community, and that made me the target for a few fucked up people. Everyone else didn't know how to handle what was going on between me and those fucked up people, and their presence usually weighed against me because, as the odd one out, they understood my side of things the least. It also doesn't help that most of the authority figures that could have done something about it were incredibly bigoted and corrupt, and thought that I deserved whatever I was getting. First, I was non-christian. This alone made me not worthy of protection. Then I got picked on, and this turned me to counter-culture. I became rebellious. Listened to the wrong music, wore the wrong clothes, etc. At that point, I was "the problem", and so the bullies had the full support of the institution.
Then I escaped that community, became close with people who had social skills and well-established circles. Things got better. Now I can handle myself in most social situations.