I see what you mean. I think the difference is, the difference between sins. Can someone be forgiven for cowardice? I think with Peter, we see that they can. With a crowd of people chanting out that they want to see God killed, what do we call that? It reads like a rejection of God from a hardened heart. It's generally understood that God does not forgive apostasy- unrepentant rejection of him and his word.

That isn't to say I think Pilate converted and repented or whatever behind the scenes and it just so happens no-one bothered to record that, I literally have no reason to believe that- but it's a question of scale. The sin of the pharisees was to reject the Messiah- emphatically and without remorse- and Pilate's sin in this instance was not doing enough to stop them. It's hard to not look at that and acknowledge that yes, everyone did sin here, but it's pretty clear that one of those was far, far worse than the other.