1. YES. Because God is still holy, and he still says ‘Be holy because I am holy.’ [Leviticus 11:44,45; 19:2; 20:7,26; 1 Peter 1:15.16]. 'Holy' means 'set apart'. God has set us apart to be his own uinque people, distinct and different from those who do not believe in him.
2. YES. Because we are children of our heavenly Father, who says to us ‘Be perfect as I am perfect.’ [Matthew 5:43-48]. As children of the heavenly Father he commands us to express his nature. See also Ephesians 5:1.
3. YES. Because sin is still sin. [ Romans 6:12-14; Colossians 3:5-8]. Getting saved, becoming a Christian, does not change the nature of sin. Our sin and our sins are forgiven through the death of Christ, but they are still sin, and therefore still offensive to our holy God, and totally out of place in those who identify as his children.
4. YES. Because the cross of Jesus Christ makes it abundantly clear
The death of Christ on the cross demonstrates, once for all, that sin is absolutely repulsive to God, that in justice sin must be punished, and that punishment is extreme. Paul points out in the Ephesians reference that it is totally out of place for believers to continue to commit the sins for which those who are not believers still face God's judgement.
5. YES. Because a person who thinks that it doesn’t matter if they sin, has not begun to understand:
Study the references in the dot points above and allow the Word of God to impact you with the utter wrongness of sin demonstrated by the truths in these verses.
FOR THE CHRISTIAN, SIN IS FORGIVEN - BUT IT IS NEVER OKAY!