You’re right to be skeptical of your friend’s views — because God never tells us to do anything that He has clearly forbidden in His Word, the Bible. God does not change, and neither does His Word.
After all, one reason God has given us His Word is so we can know what is true and right — and also what isn’t true and right. If it was wrong to murder or steal or commit adultery when God gave the Ten Commandments to His people over 3,000 years ago — then it’s still wrong. If it was wrong to reject Christ and nail Him to a cross 2,000 years ago — then it’s still wrong. As the Psalmist wrote, “The law of the Lord is perfect…. The statutes of the Lord are trustworthy” (Psalm 19:7).
Pray for your friend, that he will realize the moral and spiritual dangers he faces by rejecting God’s Word and giving in to the world’s relativism. Perhaps he’s struggling with a particular sin in his life, and is seeking to excuse it by claiming God doesn’t care. Or he may be anxious to win the approval of others and not appear “narrow-minded.”
Whatever his reason, ask God to help you be a witness for Christ to your friend — not condemning him, but being an example to him of Christ’s love and truth. The Bible says, “Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone” (Colossians 4:6).