mentsch1: Yes, it absolutely is hard to believe that this was done by many chashuv rabbanim throughout history, because it simply never was. No chashuv rabbanim have attended a Christian prayer service in a Christian church where they bow down to yushke and pray to him. No matter what the reason or excuse. No matter if it was the King himself who directly ordered him to or not.
Do you remember the story of Chana and her seven sons? Jews do not enter the sanctuary of a church for a prayer to Avoda Zora.
Throughout history Yidden have rather given up their lives and allowed themselves to be killed rather than do such a horrendous thing.