Even before these scientific studies, there was a concept known as "mirroring." In mirroring you see yourself in the way the other person treats you. If you can make them laugh and smile, you see yourself as a comedian in their reaction.
If people mirror good qualities back to you, that's a good thing, especially for children.
Now what if all you get mirrored to you is contempt and other bad qualities.....especially from a young age? What if you get it from schools, and media, and other people?
If it's bad enough, it can create humiliation followed by the desire for revenge. It reminds of a comment from William Blake, that violence is just love distorted ("I am drunk with unsatiated love, I must rush again to War...").