The effect of this statement is to create a feeling of disgust in the reader in relation to the colonists.
Explanation:
When Ceremony affirms that the colonists are the fruits of witchcraft, he gives the reader a feeling of discomfort about the colonists' existence. Just as witchcraft is something that causes us discomfort because it refers to something portrayed as bad in our culture, Ceremony's statement wishes to emit this same meaning in relation to the colonists.
