"Do I now persuade men, or God? Or do I seek to please men? For if I still pleased men, I would not be a bondservant of Christ."
Paul's goal in his witness was to persuade people that Jesus is the Way. But how could he do that, if he was okay with the idea that there were many valid, different gospels? The answer to his first question is, "Yes, Paul, you do intend to persuade men to believe the gospel." You cannot persuade God to go along with a false message. You cannot persuade God to accept heresy! So why try to talk God into endorsing your witness, if your witness is untrue? Paul's strong insistence on a single, fixed, unchanging gospel gives him a message he can persuade someone to. You cannot "convert" someone to a cloud of religious haze. Paul's rock-solid stance on the gospel was essential for his persuasiveness.
But next he asks a reverse question. Is he a people-pleaser? Is he a chameleon? Did he change content of his witness, in order to flatter the listener and avoid trouble? The answer to this question is no. Perhaps some people thought Paul was a shape-shifter, because he tried to understand the local cultures of the people he served. They might have accused him of being a compromiser, because he adopted Gentile style when he was with Gentiles, and Jewish style when he was with Jews (1st Corinthians 9).
But when push came to shove, Paul clearly said this: there is only one God. There is only one Savior, God's eternal, incarnate son Jesus Christ. There is only one basis for forgiveness, the cross. There is only one condition to meet, in order to receive God's forgiveness, and that is faith. And anyone who teaches some message other than this is under the curse of God.
These are not the words of a shape-shifter, are they? They are not the words of a man who took a poll, conducted a survey, wet his finger to test the direction of the wind, and then sculpted his witness to please a crowd, are they? No indeed!
Paul was not the kind of man who deliberately tried to poke his finger in people's eyes with his teaching, unlike some angry 'fundamentalists' one can hear. Paul wasn't a ranter. But he had a God-given message, and he would not sway from it, and he wouldn't cloud it up with artfully vague talk. He was the type of man that religious cultists and skeptics hated, because he was clear, he was firm, and he was unapologetic.
Do we sculpt the Christian message in order to build numbers and avoid conflict? If so, then we are not servants of God.