I teach RCIA - that's a major part of my job.
RCIA candidates and catechumens always have one question: why is God so mean and angry in the Old Testament, but kind and gentle in the New?
My standard explanation goes thus:
When I was young, my parents put me in the corner. If you asked me, at five years old, why they did that, the answer would have been obvious - they hate me and are angry with me.
Now that I'm 45 and putting my own children in the corner, I realize that it isn't about anger. In fact, what the kids do is sometimes so funny it's hard to stop laughing. But I can't allow them to think such behaviour is acceptable, or they'll have real trouble as adults. So, even as I'm putting a frown over my grin, they are getting dissuaded from their actions.
The people of the Old Testament did not have the fullness of grace made available to us through the Incarnation. As a result, the Old Testament is written by the spiritual equivalent of a five- year old having a bad hair day.
And as I was giving this explanation, I realized something. The difference really IS in attitude.
Look at St. Paul for instance: scourged, beaten with an iron rod, stoned (possibly even to a near-death experience, since he talks about being caught up into the third heaven), and ultimately beheaded, he was treated as badly as any Old Testament prophet you care to name. Yet not once did he claim that God was pouring out wrath upon him. Instead, he kept insisting that God is love.
Indeed, the pre-eminent promoter of this "God is Love" philosophy, St. John, was boiled alive in oil and survived, yet his three letters are all about ... God is Love.
Is it a coincidence that the same John who wrote those letters is ALSO the John who recorded - uniquely recorded - that Jesus not only cleansed the Temple, but braided a whip of cords first in order to improve the experience for the people being thrown out?
Try this on for size.
Read any of the Gospels and pretend that God may not be love. Look for signs of love in the things Jesus says and does. If love means being nice, Jesus ain't love.
He calls the Pharisees and Sadducees every name in the book, including references to their burning in hell. He calls one woman a dog. He beats people with a whip. Even the apostles are essentially treated as dimwitted rubes most of the time.
In short, Jesus in the New Testament really doesn't act much differently than God does in the Old Testament. The apostles are certainly not treated any more kindly than the prophets were. The only difference between the two testaments is this: God dies in the second one.
We all agree that the God of the New Testament is Love, and are all concerned that the God of the Old Testament is Not.
We don't understand His Love until He dies for us.
Once we see that, everything falls into place.
We start to understand that the bad things which happen to us are not His doing, but ours.
We begin to realize that He's been trying to keep us out of both the frying pan and the fire, and we just won't accept it. We insist on abusing ourselves and each other instead.
It isn't that the God of the Old Testament hates us or is angry with us.
It's that we hate us and are angry with ourselves.
As John Paul II pointed out, God revealed man to himself.
This is how we know God is love.