Why did Paul have to defend his apostleship to the Corinthians?
Paul defended his apostleship because the Corinthian believers were carnal and had come out of a city marked by idolatry and immorality, yet still felt drawn back to that old life. Especially the Jewish element challenged him as an imposter who had not walked with Jesus or spent three years with Him like Peter.
Les explains that in 1 Corinthians 9 Paul is again defending his apostleship to these carnal believers at Corinth. They lived in a city of abject idolatry and horrible immorality, and though they had come out as believers, there was still a draw back into that old life. Consequently, as Paul writes, he has to defend his apostleship. Les suggests the Jewish element in Corinth especially challenged him, asking who he thought he was, calling him an imposter because he had not walked with Jesus of Nazareth or spent three years with Him as Peter did.