1 Thessalonians 5:15
See that none render evil for evil unto any [man]; but ever follow that which is good, both among yourselves, and to all [men].
Note 12 at 1 Th. 5:15: The word "see," as used here, means "to make sure" (NAHD). Paul is instructing the Thessalonians to make sure that everyone is treated fairly.
Note 13 at 1 Th. 5:15: Paul is instructing the Thessalonians to treat ALL men in a godly fashion. There is no double standard in Christianity. Galatians 6:10 says, "As we have therefore opportunity, let us do good unto all men, especially unto them who are of the household of faith."