It is the quietest and meekest people who are often capable of the most sudden and unexpected violences for the reason that when their control does snap, it goes entirely. (Hercule Poirot)
... the belief in a superstratum of human beings ... is the most evil of all beliefs. For when you say, 'I am not as other men' -- you have lost the two most valuable qualities we have ever tried to attain: -- humility and brotherhood.
Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]