Paul the Apostle's scathing words upon the propagators of a works centered Gospel were indicative of one whose only desire was to please God. Paul's days of attempting to be agreeable at the expense of God were over. His relationship with God was real, and this was some of the proof in his life to that end. He would not compromise the clear teaching of the Word of God.
For Paul to mention "pleasing" men, there must have been an accusation toward him. Perhaps it was his message of the Gospel that seemed to "easy" to receive, a Gospel that did not require that one work for it in order to gain God's favor, but only believe with the heart. Surely those who troubled the church at Galatia felt that man had to contribute something in order to be saved or to make God happy. Paul's Gospel stood diametrically opposed to their false Gospel. As a result, they learned that Paul was no man pleaser.