Why do so many people, even Christians act so vain?
People are naturally vain because everyone is naturally proud. Pride is the sin from which all other sins spring. When a person becomes humble through the power of the HOLY SPIRIT, he will lose his vanity. The key to ridding yourself of vanity is to humble yourself.
The way we do that is through daily prayer (Luke18.1l Ephesians 6.18; 1 Thessalonians 5.17), disciplined, daily Bible reading (Deuteronomy 17.9; Revelation 1.3), studying the Bible daily (Proverbs 8.34; John 5.39; Acts 17.11; 2 Timothy 2.15), memorizing Scripture daily (Deuteronomy 6.6; Psalm 37.31; 40.8; 119.11; Proverbs 2.1; 3.1; 4.1; 8.21) and meditating on Scripture daily (Joshua 1.8; Job 23.12; Psalm 1.2; 119.15, 23, 48, 78, 99, 148).
We also should fellowship with the brethren as often as possible (Acts 2.42, 46-47; Hebrews 3.13; 10.24-25), share the Gospel as the HOLY SPIRIT leads (Psalm 96.2; Acts 2.47; 1 Peter 3.15) and make disciples (Matthew 28.19-20; 2 Timothy 2.2).
Why are some people called "wicked?"
The wicked are wicked. They commit every sin imaginable and they enjoy sinning. They destroy the lives of those around them by their murders, rapes, pillaging, plundering, stealing, lying, bearing false witness, getting drunk and high, slandering others, causing dissension, giving and taking bribes, rioting, revolting, starting wars, mocking God and His Word, taking the name of Jesus in vain and using His holy name as a curse word, blaspheming the HOLY SPIRIT and committing hundreds of other sins.
Those who die in their sins will be judged, found guilty and cast into the Lake of Fire where they will be punished for those sins throughout all eternity (Revelation 20.11-15; Matthew 25.46).
Yet even though the wicked are evil and sinful so are Christians. Some people are worse than others. Every true believer was a wicked person to some degree before they were redeemed: by the blood of Jesus (1 Peter 1.18-19). We were no different and all of us were headed straight to hell. It was only by the grace of God that He saved us. All Christians must love the wicked with an undying love as our Savior commanded:
"But I say to you love your enemies, bless those who curse you, do good to those who hate you and pray for those who despitefully use you and persecute you" (Matthew 5.44)
Christians must love the wicked because we do not who will be saved and who will not. God brings some people to a saving faith in Jesus Christ by the love Christians show to them. If we were living in the first century A.D. most of us would have hated Saul of Tarsus because he was the number one enemy of believers. We would have been wrong in hating him. This is why we are commanded to pray for all kinds of people:
"Therefore I exhort first of all that supplications, prayers, intercessions, and giving of thanks be made for all men, for kings and all who are in authority, that we may lead a quiet and peaceable life in all godliness and reverence" (1 Timothy 2:1).