To respond to this question we need to refer to the information that Miller gives us about Rebecca and Francis Nurse and the way in which they feuded with the Putnams. We need to remember that whilst the good opinion surrounding the Nurses was so high, at the same time, the fact that they engaged in a land feud with a Putnam indicates that they had made some enemies. It was a perfect opportunity, therefore, to use the atmosphere of fear and terror to strike back at somebody who under normal circumstances would be completely unviolate. Consider what Miller tells us about this land dispute:
Another suggestion to explain the systematic campaing against Rebecca, and inferentially against Francis, is the land war he fought with his neighbours, one of whom was a Putnam... As for Rebecca herself, the general opinion of her character was so high that to explain how anyone dared cry her out for a witch--and more, how adults could bring themselves to lay hands on her--we must look to the fields and boundaries of that time.
Even for figures as respected and as important as the Nurses, the cries of witchery were the perfect opportunity for bitter individuals to settle nursed wrongs that had been existence for a long time. The fact that the saintly Rebecca is accused of witchery just shows us how strong the suggestion and power of fear can be in ruling our actions.