People are, indeed, terrible. It's disturbing to think that most "good people" simply lack the opportunity to do the most terrible things one can imagine.
One event that made me rethink things was a recent wave of school shooting in Brazil. One happened, and then several others followed.The media stopped reporting, afraid of a "copycat phenomenon", but no one talked about the fact that there are lots of people in their homes who want to enter a school and exterminate others, but simply lack an "incentive" to do so.
Now think about everything. If there wasn't any punishment for crimes, everything would be "solved" by killing, sexual abuses would happen all the time, among other things, just like a few thousand years ago.
Another event that made me rethink my worldviews was them the police went on a strike in a brazilian state, about 6 years ago. The place turned into chaos, as people robbed all places they could.
If you look into historical events, like the belgian's bloody regimen in congo, with leopold II, or the sino-japanese war, you will see the atrocities people are capable of.
It's disturbing that all of that is embedded in people all around us, just waiting for an opportunity to act...