The problem is, depending on the environment and personal positions, kindness isn't necessarily the most useful option, and even if everyone likes it, kindness doesn't necessarily sustain itself.
The most important new information about aggression I've got in years is from Prof. Robert Sapolsky's lectures on Human Behavioral Biology. Mind blowing, totally recommend you watch it on Youtube.
In the conclusion to his 4-lecture series on the subject of aggression (https://youtu.be/BqP4_4kr7-0?t=6081), he says:
We have this general notion that if we are rational, if we are learned, if we are scholarly, if we respect thoughts and truth and all of that, we will make the world a better place.
All of us who are professorial have somewhere in there this totally ridiculous belief that if you're allowed to lecture at a subject long enough, it will give up and go away. And that will be the cure for the world aggression. If everybody could be lectured to about the frontal cortex, it will solve world violence. But the basic problem is that aggression is such a messy set of behaviors.
Schizophrenia - no question about it, bad news. Alzheimer's disease, childhood cancer, global warming, all of these unassailably bad news. But aggression is a whole lot more complicated, because of that point where we started with, which is, the same exact behaviors, and depending on the context, it could be something that would get a medal for someone, someone you will want to mate with, vote for, reward, cheer on, join in. And in another setting, it is the most frightening thing that can happen to us. And it's the same behaviors in all those cases.
And it's for that reason, that violence is going to be the hardest subject for us to understand biologically. And it's for that reason, that it's always going to be the one we have to try hardest to understand.