The behaviour that you are trying to map is not fully explained in the experiments. human beings like to be just and fair.
The bonding that you mention happens in favour of someone who has not been treated fairly and against the person who was not just and fair.
Cruelty by nature is not a human trait.In reality this is nonexistent. Trying to protect oneself and other human beings is the natural behaviour. When culture because of improper understanding does handout cruelty as a way of life human beings feel bad from the inside and over a period of time a few generations get rid of that practice.
This is the process of natural evolution . If if we look beyond the simple experiments cited in your article with a Holistic view you will find acts of just behaviour and bonds built on love to be far greater than the ones built by hate.
Hate per se is not a characteristic of human beings and it is the fear that gets manifested as hate and any human being can validate it.
Positive traits are the reality and their absence is the incomplete understanding of the self. This is what we need to propogate to get people to enjoy their existence on the planet.