Survival crisis

People are of the self, selfish, on the selfish nature, complete self maintenance. No matter how social development, the society always relies on the strong bullying the weak, the weak is always being bullied. But for children, it really is innocent. One day, out to play with her children, bought an ice cream, children did not eat a few mouth, was robbed to older children, while other parents gloat. What is this point of view, may is a public robbery?