One of the many problems with the classic "Penal Substitution Theory" of atonement* is that it tends toward an a-historical understanding of Jesus and the cross. On this issue I have found Gregory Love's writing quite informative and I'd like to share it here:
By moving from an historical to an a-historical view of how Jesus saves us, penal substitutionary theory folds violence into saving motifs in the God-image, against the intentions of Jesus. It understands the divine-human relationship through an abstract legal formula, allowing it to locate the salvific work of God solely in the cross. By focusing on supposed "universal" principles - sin as disobedience; the need for retributive punishment punishment before divine forgiveness is possible; the saving role of an innocent substitute - rather than the concrete elements of the gospels' narrative involving Jesus' birth, message and ministry, execution by an empire, and appearances after the resurrection, the political elements in Jesus' statements and actions, death and resurrection can be ignored, as can the theorist's own political interests. Jesus' consistent nonviolence becomes irrelevant to the atonement model, and fails to inform its God-image.
* the theory that human beings are sinful and deserve to die/suffer forever (or any form of this) so God had to have someone die and decided to have God's own Son die in the place of human beings, thereby taking on the penalty of death.