I understand why someone might look at all the pain and suffering and cruelty in the world, and ask that question. If God is love, why would a loving Father allow His children to suffer? ...Or, at the very least, why not stop some of the very worst attrocities?
My dad once said that when he became a new parent, he discovered a whole new capacity for love, like a new heart that he'd never used before, but had been saved just for this purpose. That's exactly what it's like.