I definitely believe the movie was about the power of forgiveness and God's forgiveness. Although it's never stated, something gives me the impression that Graham truly forgave Ray Reddy at the end of the movie. His attitude after his son recovered from the asthma attack in the end was one of forgiveness and warmth. I think the movie was not just about perseverance, but also forgiveness.
What a load of nonsense this movie is. The whole premise of it is that there is life "out there" which is obviously vastly more intelligent than human life (intelligent enough to travel trillions of miles through space). These intergalactic geniuses have one Achilles heel - water. It kills them. So what do they do? Out of all the planets in all of the solar systems in all of the galaxies in the universe to invade - they choose one that is 70% water. Duh! It is about as convincing as all of the wrecked spaceships containing alien bodies that the government has hidden away in secret research facilities - they can make machines to carry them across the galaxy or perhaps even universe to get here, and they don't think to check the brakes before they leave?