Possible Clues:

• One who tends to think the worst of others
• Fallacy nicely traps one disinclined to believe
• Some kleptocracy — nicking? One believes the worst
• Pessimistic sort
• Glass-half-empty type
• One who thinks only self-interest motivates people
• 'A man who, when he smells flowers, looks around for a coffin,' per H. L. Mencken
• Member of a school of Greek philosophy
• Bankruptcy nicely protecting a scoffer
• Scoffer