Nicely said. Why else would one ‘celebrate’ mass if it were anything less then the full and perfect sacrifice of Christ? But that are some pretty sick ideas of theology around here; take post 26 for example - someone’s idea of God is He who leads people away from the truth. When people have been indoctrinated that perversely, it’s difficult, if not impossible, to talk sense to them.
If it is an “ongoing” sacrifice, then it is NOT FINISHED. It cannot be both ways, by definition. Does your church believe/teach that Christ paid the FULL PENALTY for sins?