It seems to me that a common feature of the vocal support for penal substitution (and it is seen a lot in Pierced For Our Transgressions) is to take Biblical texts that describe the atonement and interpret them as supporting only penal substitution. It is true that some support substitution. However, it seems to me that many of these do not require penal substitution (not even substitution) as a model of atonement.
Take this recent post by Adrian The Atonement – Romans 6-7 and Penal Substitutionary Atonement. I do not understand why Adrian believes this text requires penal substitution.
I do agree with him when he says:
note the link Paul makes between Jesus’ resurrection and our empowerment to bear fruit for God.
but these texts point to issues common to all theories of atonement eg
We know that our old self was crucified with him in order that the body
of sin might be brought to nothing, so that we would no longer be
enslaved to sin
says nothing about Jesus being punished for this to happen, it says nothing about a legal justice transaction. Also it seems strange that in
Likewise, my brothers, you also have died to the law through the body of Christ,
Paul is writing about Christians having died to the law. That seems an unlikely argument for a legal understanding of the cross.