The Pope never told any of us to sin. Your example is not anything like reality. Besides if the Pope told us to sin, he probably wouldn’t be Pope anymore.
A Pope would not cease to be a Pope for telling someone to sin. That would be a sin on the part of the Pope, but sin does not result in a Pope ceasing to be Pope. At most, only public manifest heresy will cause a Pope to loose his office, and even that is debatable.
I don’t think you know what “objectively mortally sinned” means. It is not the same as committed an objectively immoral act, which is what I hope you meant to say.
Objective mortal sin is the theological term. It refers to the act itself, rather than the guilt of the individual. Subjective sin pertains to the guilt; objective sin to the act itself.
Your whole drudging up of what happened once in Assisi is, well, silly. There is no moral law that forbids Catholics from allowing non-catholics to worship in a room that they own.
Let’s say that a Catholic
invited an abortion doctor to their Church and asked him to please perform an abortion in a particular room in the hope that God would grant world peace. Would that be a sin on the part of the Catholic? Of course it would, since the Catholic encouraged the sin. The only difference between that and Assisi is that, objectively speaking, sins against the first commandment (false worship) are more serious than sins against the 5th commandment (murder).
Kind David committed the sin of adultery and was forgiven by God. Solomon encouraged and took part in false worship and, as a result, God divided the kingdom.
*“And Solomon did that which was not pleasing before the Lord, and did not fully follow the Lord, as David his father. Then Solomon built a temple for Chamos the idol of Moab, on the hill that is over against Jerusalem, and for Moloch the idol of the children of Ammon. And he did in this manner for all his wives… and burnt incense, and offered sacrifices to their gods. And the Lord was angry with Solomon… And the Lord therefore said to Solomon: Because thou hast done this, and hast not kept my covenant, and my precept which I have commanded thee, I will divide thy kingdom.” (3 Kings 11:1-11)
Sins agains the first commandment are very serious. If you read the Old Testament you will see the Jews falling into this error over and over again. God would punish them, and they would turn back to God. One example is found in 1 Machabees 1. After discussing this example, Pope Leo XIII said that what happened in the Old Testament often prefigured what was to happen in the New.
Although the Church has always taught that false worship is a sin against the first commandment, nevertheless, John Paul II
encouraged it at Assisi. That is beyond mere liberalism.*