You didn't include the full context.
5 Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ. 6 Obey them not only to win their favor when their eye is on you, but as slaves of Christ, doing the will of God from your heart. 7 Serve wholeheartedly, as if you were serving the Lord, not people, 8 because you know that the Lord will reward each one for whatever good they do, whether they are slave or free.
So for example, we are still modern slaves. But even to your boss, teacher, or leader, you should still show some respect to their face because everyone wants some respect. If you earn their favor, they are more likely to find God and be open to His words. Same way Daniel respected Nebuchadnezzar even though Nebuchadnezzar was a massive retard. Daniel would interpret Nebuchadnezzar's dream and even Nebuchadnezzar put his face to the ground and said how powerful Daniel's God is. Or you can just call a tyrant a fag to his face and risk getting killed, honestly up to you.