The Authorized Version (also known as the KJV) translates 1 Thess. 5:22: "abstain from all appearance of evil." Honestly, it is a bad translation of the Greek, which is why all of our modern translations today (including the NKJV) use a phrase like "abstain from" or "stay away from every form of evil." The Greek has nothing to do with "appearance" but rather a "separation from." Most likely the church culture of the day was trying to use this verse to enforce some of their legalistic tendencies. When it came to accusing someone in the early church of sin it was often a "guilty" before proven innocent type charge. There was very little, if any, grace. (Hence the witch hunts of the late 1600s) Unfortunately, as the KJV was translated they allowed their theological views to sway the translation to fit their views. (every translation is somewhat guilty of this, but this is a perfect example.)
Jesus obviously didn't care too much about avoiding "appearance" when He had dinner with the tax collectors and sinners at Levi's home. Now, before I through the baby out with the bathwater, I do think there is biblical precedent for living "upright" lives as an example for non-believers, but certainly not to look down at them. (which is always a danger we must avoid) The point is to show love and grace to "sinners" so that they will be drawn to Jesus, not so that they will be pushed away by our pious attitudes. We can NEVER expect a non-believer to live like a believer, because they are not one! Unfortunately, many churches (and Christians) today seem to quickly forget that truth.
Here are just two (of many) passages that support the admonition of living "upright" lives among the world.
Ephesians 5:3 says there must not even be "a hint" of sin. (NIV) It then goes on to list several examples of sin. There are actually only two Greek words that are translated as the phrase: "there must not be even a hint of." One of them means "speaking or mentioning the name of." Obviously, it doesn't mean that we can't say the words "sexual immorality" or "greed." Rather it means these things should have no consideration in the life of a believer. The actions/thoughts related to these sins should be avoided at all costs.
1 Peter 2:12 says, "live such good lives among the pagans that, though they accuse you of doing wrong, they may see your good deeds and glorify God on the day He visits us." (NIV) Christians are to abstain from sinful desires not only for their own spiritual well-being but also in order to maintain an effective testimony before non-believers. Does that mean that when we live upright lives the non-believing world around us will always approve of our actions? Not at all. Later in 1 Peter 4:4 it says, "they (non-believers) think it strange that you do not plunge with them into the same flood of dissipation, and they heap abuse on you." The only time that the sinful world will approve of our "good deeds and glorify God" is "on the day He visits us." So, until THE DAY, when every knee bows and every tongue confesses that Jesus is Lord to the glory of the Father (Phil. 2), we can expect our "good deeds" to be "rewarded" by strange looks, obscene comments, and criticism by those focused on worldly things.
(another passage would be Philippians 2:14-15: "that you may be blameless and innocent.")
The point is: we need to be salt and light. We cannot be salt and light if we live exactly like the world. We are called to be different. If we aren't different then what good are we. (see Matthew 5:13-16)
One last warning from Colossians 4:6: "Let your speech always be gracious, seasoned with salt, so that you may know how you ought to answer each person. " Be different, but be GRACIOUS!
Our Savior is born, Jesus; the only name given under heaven by which men must be saved!