If the pope is standing and representing the word of Jesus or God until one or both come back to earth why you would put the pope who is a man in charge when man killed your son?

Answer 1

The Pope does not represent Jesus or God. The function of the Pope is to lead the Church. When Jesus said that he was placing his church on Peter, he was discussing how men would lead communities devoted to becoming united with God. As a result, the Pope is an intermediary, focusing the people's attention toward God, but not representing Him or the people.

As for Jesus' expiation for humanity, Christianity holds that this was Jesus' intent from the start and therefore, men as a collective should not be guilty of the sin of murdering Christ since it was that execution that allowed Jesus to redeem mankind.

Answer 2

Catholic Answer:
The pope is a bit more than a simple 'intermediary'. Catholics do consider the pope to be the Vicar (representative) of Christ on earth. As per the Catholic Encyclopedia:

"In the course of the ages other vicarial designations have been used for the pope, as Vicar of St. Peter and even Vicar of the Apostolic See (Pope Gelasius, I, Ep. vi), but the title Vicar of Christ is more expressive of his supreme headship of the Church on earth, which he bears in virtue of the commission of Christ and with vicarial power derived from Him. Thus, Innocent III appeals for his power to remove bishops to the fact that he is Vicar of Christ (cap. "Inter corporalia", 2, "De trans. ep."). He also declares that Christ has given such power only to His Vicar Peter and his successors (cap. "Quanto", 3, ibid.), and states that it is the Roman Pontiff who is "the successor of Peter and the Vicar of Jesus Christ" (cap. "Licet", 4, ibid.). The title Vicar of God used for the pope by Nicholas III (c. "Fundamenta ejus", 17, "De elect.", in 6) is employed as an equivalent for Vicar of Christ."

I am the first to admit that not all popes have conducted their lives as a true Vicar of Christ. However, even the most vile and disgusting pontiffs who have, unfortunately, filled the shoes of Peter, not one of them taught or promulgated a single doctrine that was contrary to the teachings of the Church. Sort of the ultimate "Do as I say, not as I do."