Salam Alaykom Sister!
I was once a Christian (hard core) and I know very well how Christians react towards others systems of beliefs. Unfortunately they are so indoctrinated towards the teachings of the trinity.
Ok, so this is the philosophy of Christians with their stubborn idea of the trinity.
Adam and Eve sin caused humanity to be "separated from the grace/mercy of God" according to biblical scripture ( i forgot the actual verse but its in there hehe) As a result of eating from the forbidden fruit... they knew they were naked so they needed to kill an animal to hide or conceal their sin.. and thus the tradition in the Jewish scriptures of sacrificing an animal, such as a lamb ( notice the symbolism lamb= white, innocent and pure)
Oh ! but wait.. God had it all planned according to Christians.. because God then decided to send "his son" (astaghfirullah) which to Christians represents that innocent, pure "lamb" who would redeem the whole world..
of all their sins not only concealing them.. but cleansing them completely. Therefore the tradition of sacrificing animals is no longer of God's interest ( which of course it never was to begin with but only according to the Judeo-Christian tradition)
So, you can see why they revere Jesus so much.. because yes indeed he was a humble man but somehow they developed this notion that God is capable of possessing this virtue of humility.. It is indeed a very good virtue, in fact it is the opposite of arrogance, which we all know is the evil sin that Iblis committed. But what a Christian must realize is that God or Allah (subhan wa taala) is arrogant or in neutral terms, prideful !.. Why? Because to whom God needs to humble himself to? No one. Is He not the All Knowing and the All Powerful ? Allah subhan wa taala is Perfect, and as the perfect being he is, he does not need to feel intimidated or inferior in order to please someone else. On the other hand, humility is a virtue that only humans posses and is what Allah subhan wa taala expects from us, his slaves, his creation.
Anyone who tries to posses a virtue of God, ( The Creator, The All Knowing, The Compassionate..ect) is committing shirk and kufr because no one can be like him, and so in the case of Jesus in Christianity, the Christians believe that it is possible for an Omniscient Supreme Being to share is divinity with a human being..
So, you can explain this to the Christian Pastor, I am pretty sure he will be stunned.. Say that the story of God humbling himself and becoming human in the form of Jesus to save the whole world.. is a nice story of love for humanity but then say why you believe it is flawed.. Tell him that in the beginning, God as the Merciful being he is.. decided to forgive Adam and Eve of their sins and thus the real tradition of repenting, then just submitting to God (swt) alone with no partners or sons or daughters is what He really intended for humanity
This is only if you desire to send the message of Islam.. if you feel this will incite a debate and not a decent discussion.. then stay away from doing so and just simply politely tell the pastor that you have no intention of discussing religion in the work force..
Asalamu Alaykom ukhty and I hope you will not encounter any problems inshallah