For do I now persuade men, or God? or do I seek to please men? for if I yet pleased men, I should not be the servant of Christ.
Note 12 at Ga 1:10: Paul was stating, "I'm not preaching man's gospel. I'm not trying to please man." The Greek word for "persuade" here is "PEITHO," and it means "to win over, and render friendly to one's self" ("Galatians in the Greek New Testament" by Kenneth S. Wuest). Paul was not trying to win people over and make friends by preaching what people wanted to hear. If that were the case, he would not have been a true servant of Christ.
Paul stated in 1Th 2:4, "But as we were allowed of God to be put in trust with the gospel, even so we speak; not as pleasing man, but God, which trieth our hearts." As a "servant" (this verse), Paul had only one master, and that was Christ (Mt 6:24). Therefore, he spoke only the message the Lord laid on his heart.
All of this was being said to make the point that the Gospel Paul had brought to the Galatians was directly from God, not man. He elaborated on this point all the way into the second chapter. The reasoning was that if God truly gave Paul this message, then there could be no room for change. The Lord is always the same, and His message never changes.
Likewise, there is no room for a gospel today that fits the culture we live in. It's the same Gospel Paul preached--the power of God unto salvation today (see note 1 at Ro 1:16). Methods can change, but the message must remain the same.