Christians -- people who bank their hopes on Jesus and spend time with Jesus and obey Jesus -- should stand up in public and tell God's truth as they see it without worrying that secular listeners may not even agree with our most basic assumptions.
Isn't it amazing how Peter and John respond to the rulers (Acts 4:13–20)! The rulers tell them to get out and not to speak in the name of Jesus any more. Then in verse 19–20 they say, "Whether it is right in the sight of God to listen to you rather than to God, you must judge; for we cannot but speak of what we have seen and heard."
One of the great obstacles to our speaking out in public about the truth as we see it with Jesus is that we think we have to win. Or we think we have to operate with the assumptions of secular leaders. But Peter shows us that this is emphatically not what we have to do. Our calling is not to win or to borrow the assumptions of the world. Our calling is to stand up and tell it like it is in the eyes of God.
[Read the rest of the article at Desiring God.]