Well, there are certainly plenty of examples for you to chose from! However, the really terrible ones occur in Chapter 22 and afterwards, as Mr. Brown is replaced by a more radical missionary known as the Reverend James Smith. Note what the narrator tells us about his view of the work:
He condemned openly Mr. Brown's policy of compromise and accommodation. He saw things as black and white. And black was evil. He saw the world as a battlefield in which the children of light were locked in mortal conflict with the sons of darkness.
Therefore, with this battlefield view, it is hardly surprising that he should dismiss openly some of the most important religious customs of the tribe and act against them to show the superiority of his God. And this is precisely what he does when the annual ceremony for Mother Earth occurs when he unmasks a egwugwu:
It happened during the annual ceremony which was held in honour of the earth deity. At such times the ancestors of the clan who had been committed to Mother Earth at their death emerged again as egwugwu through tiny ant-holes.
One of the greatest crimes a man could commit was to unmask a egwugwu in public, or to say or do anything which might reduce its immortal prestige in the eyes of the uninitiated.
Thus, by trying to impose his Christian cultural practices, the Christians deliberately break an incredibly important taboo which results in many problems and difficulties, and greatly raises the tension between the Christians and the rest of the tribe.