Archer's personality bares completely no resemblance to that off his Saber form. He has become a complete machine devoid of almost any personality at all, with only his one goal of defending Christianity from those who might become threats to it. Seeing him in this state is pitiful, and most of the other Servants will likely pity him after seeing what he has been reduced to. He is a broken human that simply lives to fulfill his purpose, he has no real emotions or reactions, as they are unnecessary for him to have because they will just end up getting in the way. He has become almost like a monster having no regrets and killing in the name of his idea of "Justice". Even those of his own religion will most likely become disgusted at what he has become, especially those that knew what he was like during his life. A friendly servant-master relationship is impossible, the best that they can hope for is Archer obeying them and not seeing them as a target. The only way for Archer to not see them as a threat or a target, is for them to be Christian, and then to also not commit evil deeds. Mercurius' existence in this form is the result of someone brought to near madness, abandoning everything for the sake of their ideals and what they believe is right. But instead of being a hero that saves every good person on the Earth, he has become a senseless killer that only lives to eliminate all potential threats to the ideal that he holds so dear. A simple killer for hire, a machine-like terminator with no other purpose. A truly pitiful existence.