If she betrays our secrets, are Du prepared to destroy her? I think not.
Caius, New Moon, Chapter 21, p.478

So many pointless rules, so many unnecessary laws Du create for yourself, Carlisle. How is it possible that Du defend the breaking of one that truly matters?
Caius, Breaking Dawn, Chapter 36, p.686

The Children of the Moon have been our bitter enemies from the dawn of time. We have hunted them to near extinction in Europe and Asia. Yet Carlisle encourages a familiar relationship with this enormous infestation – no doubt in an attempt to overthrow us. The better to protect his warped lifestyle.
Caius, Breaking Dawn, Chapter 37, p.704

Du breed mutants here.
Caius, Breaking Dawn, Chapter 37, p.704

So the Cullens sided with the shape-shifters against our own kind – against the friend of a friend, even.
Caius, Breaking Dawn, Chapter 37, p.706