Why injustice makes us so upset

How often does something we see on TV, or read on the internet make us mad? Somebody says something ridiculous and it sets us off. Some sense of righteous indignation or moral outrage is provoked, and we tear off into a rant on what that person had the gall to say or do in public. All of us are preachers at some level. But why is it we get so upset?
We know instinctively there are things worth getting upset about. We know there is real injustice in this world. There is real oppression, and real pain. There are multitudes of real victims who suffer under the real policies and real practices of those in authority over them. It is the responsibility of every human being, spurred on by a truly righteous indignation, to fight this injustice — beginning with the injustice we see in ourselves.
We all know the difference between right and wrong. We value and applaud self-sacrifice and service; we frown at selfishness, and punish the perpetrators of real crimes. We can all spot the difference between the delivery driver who brings our TV, and the thief who comes to steal it. In other words, there are moral standards we all live by. And it is these moral standards that determine why and when we get upset. But this begs the question: where do these moral standards come from? Some say they come from the shared commitments and values of a particular majority of society. Some say they are inherited from evolutionary developments that favor life over death. Still others say they come from above, from some kind of divine law.
You might ask, does it really matter where these standards come from, as long as no one steals my TV? Well yes, it actually does. Because if we can’t explain the nature and origin of our morals, then we have no real right to act on them. We would have no real right to call the stealing of our TVs theft at all. We wouldn’t even have the right to be upset.
Consider for a moment what it would mean for morality to exist merely as a commonly shared set of values that have no anchor or source outside of our own society. If that is the nature and origin of our morals, then what is to stop another society, or even that less scrupulous person living down the street, from having and acting on the exact opposite values? By what standard could we call their actions wrong, and ours right? If moral values begin in us, how can we call the different moral values that begin in others mistaken? Without something outside of this world, outside of this universe, defining for us what is right and what is wrong, keeping everyone in check, all we are left with is personal preference – what’s good for me, what makes me happy. The history of the last century, and the legion of crimes committed against humanity that century contained, should be enough to teach us that such a society, where “moral values” are derived from the personal preferences of the strongest, is not only undesirable, but unconscionable.
The point is this: for moral standards to actually make sense, for them to have any teeth at all, they need to come from somewhere outside of any particular person or society or era. If stealing is wrong at all, it must be wrong absolutely, meaning everywhere and at all times. Only then, because it is true without reference to how we feel about it, it binds not only our own actions, but those of oppressors and dictators as well. This is the foundation of both civilized law and government. It is the foundation of the liberties we enjoy. It is what makes a functioning society work.
As a Christian, I hold that these moral absolutes are actually reflections of the character and nature of God, as revealed in the Bible. He is the only one who exists absolutely, independent of all else. Because this is true, His law (Thou shalt not steal) holds true for every society, everywhere. And it is because we are made in His image that we instinctively know stealing is wrong. The standards of God woven into the fabric of our souls are why we have a concept of justice at all. It is the only thing that makes sense of why we get so upset.