Briefly sum up the speech Colonel Sherburn makes to the mob. What aspect of human nature does he criticize?

Sherburn's speech condemns people who are unwilling to stand up for what they believe because they're afraid. He notes the way people won't stand up in the light of day, but that they're perfectly willing to stand up in the dead of night when no one is looking. The aspect of human nature that he's condemning is the nature of human cowardice.