Because, there are two ways we imitate people in our lives. One of which is like the man mentioned above. He saw the evil deeds of another person and was planning on imitating those actions. John, the writer of four New Testament books, wrote about just this sort of action in 3 John 1:11. He told his beloved brother Gaius that he was not to follow, or imitate, that which is evil because he that does is one that does not know God and has not seen Him. Why did John write this? Well, 1) because the Holy Spirit inspired him to do so, but 2) because there was a man that was doing evil in the sight of Gaius, namely Diotrephes. Diotrephes was trying to take over the church in speaking against other Christians and kicking people out of the congregation without due process, and most likely for absolutely no Biblical reasoning. Was Gaius tempted to follow him? I sure hope not. But John saw the need to tell him to not follow Diotrephes in anything he was doing and not be a copycat of evil.
And, second, Paul spoke of a type of imitation that is absolutely necessary in the life of a Christian. That being the imitation of everything that is right. He wrote 1 Cor. 11:1 and told the Christians at Corinth to imitate him in as much as he imitated Christ. Did Paul have times in which he sinned? Yes, but he was urging the Christians to copy-cat him in the way of the Lord. Along with this goes the end of the passage we looked at in 3 John. John told Gaius to imitate that which is good because one that does good is "of God."
So, when we watch crime dramas or read the news and see copy-cats taking the horrible crimes of other people and recreating them we can see exactly how NOT to live the Christian life. But, in the same way, when we see people following the Lord without addition or subtraction we should copy-cat those people because they are helping us to see the true way of salvation.