After one of the converts kills the royal python, why does Okonkwo think it is a womanly decision to ostracize the converts from the daily rituals and privileges of members of the clan?

He believes ostracizing the converts is not a harsh enough punishment. He believes the rituals and traditions of the clan are being destroyed by the new religion, and the converts are turning their backs on their own people. His impulse is to kill the converts, ending the new religion once and for all.