And further, the fact that when urging his disciples to the exercise of kindness, the Savior says, "Be ye perfect, as your heavenly Father is perfect, who bids his sun to rise on the just and on the unjust," (Mt 5:48, 45) suggests even to a man of the smallest intelligence this most obvious meaning, that he is putting before his disciples as a pattern for imitation no other God than the maker of heaven and the giver of rain (§1).I don't want to comment on Marcionism, but rather on the apparent absurdity of being told to imitate the example of the Creator in the natural order. Typically, people complain about the apparent injustice of the natural world: the wicked get away with all sorts of evil at the expense of the innocent. Why should God's apparent laissez-faire attitude be worth copying? Most people think the fact that there aren't more frequent interventions for the sake of justice in the natural world is an evidence that there is no God.
Of course, the biblical answer to these questions is that God's kindness now is intended to prompt repentance, because there is a judgment coming when each person will get what she deserves. But there is something deeper at play in these kind of accusatory questions addresses to God. It seems to me that this desire for justice and fairness, for a clear moral order, while being good in itself and considered abstractly, is dangerous and even devilish if coupled with a sense of self-righteousness.
It's easy to desire justice in the case of others. But the biblical claim is that every person is so deeply affected by the poison of sin, in such grave danger of damnation, that it took the death of the Son of God to make atonement and win salvation for them. The person who complains about God's apparent lack of justice, then, ought to be aware of the fact that she deserves damnation, according to that justice. If a person doesn't wish her own damnation for justice's sake, neither should be quick to wish for justice in the case of others.
For this reason, I am skeptical of persons whose lives and words are consumed with an obsession for justice. Too much time spent thinking about the injustice and iniquity of others can give a person the false sense that's she's alright, that others are the problem. According to Jesus, we ought instead to be kind and wish the good for the wicked and for those who do us evil, whereas we ought to pray: Lord, have mercy on me, a sinner.