This is a rough outline for a sermon I haven't been asked to preach (that being by far the most common type).
When we look at the world, it is hard to ignore the injustice, the suffering, the inhumanity of humans to other humans. And we rightly cry out to God for justice. And the message of this Psalm is that God will hear the cries of the oppressed, the victims. He will hold the Hitlers and the Pol Pots and the perpertrators of genocides and the paedophiles to account. He sees. He hears. He listens. And he will act.
But that is only part of the story. You see, we love to think that there are good people and there are evil people, and that there's something seriously wrong with the evil people, but we're ok. But actually, when you look at it and think about it, that's rubbish. Hitler was democratically elected in Germany. If we had been German in the early 1930s, half of us would probably have voted for Hitler. The Hutus in Rwanda were people, just like us, and yet so many of them were driven by their situation to kill and main their neighbours. As GK Chesterton wrote in his Father Brown stories, we are each capable of pretty much any crime, it just depends on our background and the situation. That is why there is an increasing emphasis on restorative justice, on trying to help people break cycles of criminality and so on. Now, I'm not saying for one minute that we shouldn't condemn people who do wicked things. I think we all know that we have to condemn them. I'm saying that when we do condemn them, we also condemn ourselves.
God is ready, willing and able to act against the criminals of this world. So why hasn't he done it yet? Because when he does, it will mean utterly destroying humanity, which is of this earth.
And yet, instead of that, he comes to earth himself as a man and suffers injustice. He becomes the victim of the oppressor as well as their judge. And because he is the victim, he can then forgive the oppressors. He suffers at our hands the punishment we ourselves deserve, so that we - the wicked - need no longer stand under his judgement if only we will put our trust in him and be born again.