The first approach usually focuses on individuals who were in the public eye in the past. Young people who were not alive at that time idolize public figures from Charles Manson to Malcolm X. Whether it is a matter of rebellion, or simply not having been taught how destructive these individuals were in their day, is up for question.
The second approach, usually coming from older people, is to pick bits and pieces of individuals' personal lives, in an attempt to take the focus off all of the good works they did during their lifetimes. Sometimes it is fact; other times it is fiction.
Unlike those who practiced and preached hate and destruction, Martin Luther King both preached and practiced love, unity, and brotherhood. His goal was to build, rather than to tear down. He accomplished more during his lifetime than most other figures in American history. Individuals who look for something that is less-than-prefect about a leader are saying more about themselves than about the leader in question. They are essentially saying no one deserves the respect that they have earned.
While many schools in the United States teach about Martin Luther King, even more emphasis should be placed on this great leader. Perhaps more young people would realize he was one of the best role models there have been in recent generations.