Let as many as are bondservants under the yoke count their own masters worthy of all honor, that the name of God and the doctrine not be blasphemed.
So basically the servant was as a Christian, to be exemplary in his service, whether he had an unbelieving or a believing master. Now if you had a believing master, he may sort of resent the fact that he still is requiring this of me. After all, we're brothers in Christ and we are believers, you know. But Paul is just exhorting them to have the respect and honor of their masters.