Actio et Reactio

If a force acts upon a body, then an equal and opposite force must act upon the body that exerts the force.

 This is the third of Newtons laws of motion of classical mechanics. So broadly said:

To every action there is an equal reaction.

True, Newton meant this in a physical way and tried to explain how bodies interact with each other, but this also applies to almost everything. Physics, Biology, Economy, Medicine, and in the end, it applies to human behaviour as well.
Every action is the reasult of another action (so it is a reaction), which is the base for another reaction.

This principle is also known as causality (It is the relationship between an event (the cause) and a second event (the effect), where the second event is understood as a consequence of the first.[Wikipedia])

There is a reason for everything. Every action, every decission, simply everything is caused by some action prior to that. No matter if its conscious or not, and even no reaction, most of the times, it is a reaction as well.
Analog to Paul Watzlawick's quote "One cannot not communicate" (Every behaviour is a kind of communication. Because behaviour does not have a counterpart (there is no anti-behaviour), it is not possible not to communicate.) It is the same with reactions.

The same principle is transmittable on a global and actual Situation. Take the egyptian uprising for example. Back at the beginning of the year, the tunisians just freed themselves in a peaceful revolution. And the egypt population was upset already. They have been going more and more upset on a daily base due to corruption, heavy limitations on free speech, demographic changes (the youth of the time when Mubarak got his power is no more, and the youth of today had different values), and of course the dead and mourning over Khaled Said, answered again with police brutality (action). On the course of the people protesting, and this protests being answered in a violent way, they got more and more upset on a potential level (reaction). The result of all this, we can see today, just by looking at egypt today. 

Those two revolts with a lucky ending, were the very foundation of the Lybian uprising. But since the actions and reactions of both (Gadaffi and Protesters) were slightly different, the outcome differed as well, and of course there is always the component of chance playing a role in that.

I think this principle is valid for many more scenarios. It just seems that this principle just is not valid for politics. If politicians would take this as one of the basic principles of their act, some things might have not happened as they did, some laws, such as immigration laws, laws which are using force of security forces, and even wars would not exist.

And unless the circle of violence is not be broken, nothing will change, only more violence will be produced, producing more violence. In Gaza, the arab states, southern africa, colombia, violenc against immigrants and almost everywhere. Someone has to make a first step. 

Why this someone is not you and your neighboours? 

BE THE CHANGE YOU WANT TO SEE!

But to break it down in the end, one can say: 

Violence induces violence,

Compassion induces compassion,

Love induces love,

and all the rest of it.