There are billions of humans on this planet, and despite being taught that everyone is a special little snowflake, that is not really the case. The planet is overpopulated with humans, and as we strain the environment, every large lifeform suffers. While groups of people tend to think similarly, there is a lot of variance in behavior.
There are some humans that like to vent their anger on weaker individuals through physical or mental abuse. These people often do it in the confines of the home, but some are so confident that they willingly do it in public, knowing that nobody would care to intervene. However, there will always be individuals good enough to intervene, and we call these good Samaritans.