How does the author illustrate the hypocrisy of barbarian ethics in the book, Interesting Times?

As part of his training, Cohen is instructed by Saveloy to buy an apple from a merchant, a task that he performs grudgingly. When the merchant calls him "venerable," Cohen beats the cart owner and steals his money. Pratchett here is underlining the hypocrisy of barbarian ethics. Cohen pays for the apple with one hand, while robbing the merchant with the other hand. It is questionable whether Cohen's paying for the apple is an improvement over the Agatean's style of polite theft without payment.