Not saying atonement isn't there, but sometimes later understandings become bigger than the original intention. Think about it- the disciples are thinking Jesus is a really special teacher, maybe they even think he's the Messiah. A Messiah who then dies. They start to think about the Jewish practices of Temple sacrifice (which is now impossible by the time the gospels were written because the Temple was destroyed), and they observe that Jesus' death seemed like the ultimate sacrifice for sin. So you get that great imagery of Jesus as the lamb in Hebrews and the Good Shepherd in John.
And this isn't just them making stuff up- Jesus (at least the way the gospels depict him) intentionally chose Passover as the time to go to Jerusalem and stir up controversy. The symbolism wasn't lost on him.
But if the cross was about the sins of the world, if that was the entire purpose of the Incarnation, then I think we've missed the whole point. 1) What sort of God demands a blood sacrifice for the atonement of sin- and then decides to send a child to die? 2) What does it say about God that God can't forgive sins in any other way? Is God bound by some rule book for gods? 3) A divine suicide mission just makes no sense given the understanding of Israel or the canon of Scripture. 4) There are several places in Scripture where the notion of God demanding sin sacrifices is challenged (Psalm 50, for example). So if the blood of goats doesn't satisfy God (but a contrite and loving heart does), why do we insist that God is angry and demands justice? If you're looking for more, read some of the earliest writings about the Church, especially from the Eastern traditions. The fact that the first followers of Jesus used the fish as their symbol and not the cross should be telling. But the cross can be used to exploit. If we are wretched souls in need of salvation, which is only afforded through Jesus' death and bestowed upon us through Baptism in the Church, then who has the power? Those in charge of the Church. The over-emphasis on sin and substitutionary atonement is about guilt and control, not grace and certainly is no consistent with every other aspect of the Incarnation.
Jesus died because he pissed off the wrong (or right) people. But that doesn't mean that his death doesn't have some larger meanings as well. Think of modern day martyrs- it's the same thing: MLK, Bonhoeffer, Romero, etc. They all died because they pissed people off, and they continued their mission despite the death threats. But yet, their steadfastness to their purpose and God amplified their message even more loudly and allows their deaths to be more than sad stories about murder committed by evil people.
This doesn't diminish the idea of Jesus' death as an atoning sacrifice, but sin offering does not define what the cross was about. There are many understandings of what happened on Good Friday- and that's the beauty of metaphor and parable (which Jesus himself used all the time, so why shouldn't we say that his death can have a range of meanings as well?).
