For centuries across Europe, Catholicism taught that the Jews were guilty of deicide—the murder of Jesus. False teaching like this leads to horrible results.
The Catholic Church did not forbid keeping the Passover until AD 325. The controversy over Passover or Easter boils down to following Scripture or Roman tradition.
Is Matthew 27:25 a Jewish admission of deicide? Rightly understood, it is absolutely not a curse. God has not bound Himself to chastise Jewry as a whole.