well i think that he is holding the keymaker because the architect needs the keymaker for his designs, but since i think that merovingian is a program that has been replaced he holds a grudge against the architect.
and filled with wrath and despair he mounted upon Rochallor his great horse and rode forth alone, and none might restrain him. He passed over Dor-nu-Fauglith like a wind amid the dust, and all that beheld his onset fled in amaze, thinking that OromŽ himself was come: for a great madness of rage was upon him, so that his eyes shone like the eyes of the Valar.
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That is what he is "programmed" to appear to do. All is for the benefit of Neo's development. He had to chase down the Keymaker which would lead him to the Architect. Of course, Neo doesn't know this fact. He doesn't even know of the Architect at this point. All was designed to steer him in that direction. He had to find to door to his further development. The Architect is the last important hurdle.
It is a trinity in itself... The Oracle led him to Merovingian who has the keymaker, and that encounter led Neo to the Architect.