In this classical Chinese, the reason why "all guests are ashamed" should mean that when talking with He Yangling, the guests did not answer fluently and the conversation was not smooth. Yang He Ling asked about his pretentious and boastful remarks, as well as his disrespect and insult to his guests. This hypocritical and arrogant attitude aroused the guests' resentment and dissatisfaction, so when He Yangling boasted about his talent, the guests felt ashamed and didn't know how to answer.
Therefore, the reason why all customers are ashamed is because of Ling's hypocrisy and arrogance, not because of the topic of pork.