The article itself points out that most of these children have been abused:
Lonique Pritchett with The Children's Assessment Center said, "Most of the time when children are touching other children, it's because they have been victims themselves and they're only acting out what has happened to them on their peers."
Pritchett has treated children as young as three years old. Almost half of the center's caseload is juvenile sex offenders, the majority of whom have been victims themselves.
To be honest with you I'm not buying vague data from the "Children's Assement Center". How is "victimization" defined - is it any different from the militant feminist definition of "rape"?