Pastor Paul is perplexed over the presumptiveness of people of a pugnacious persuasion who consider themselves to be in a position to pass over the Gospel.
Paul's genesis as an apostle is established by Christ, not by man. Therefore, the gospel Paul preaches can be trusted to be the gospel of Jesus Christ.
As Craig and Troy crack open the book of Galatians, Saul the Christ-hater becomes Paul the one sent by Christ. He knows what gospel is, so why have the Galatians forgotten?