To oversexualize is to persuade a child to take notice of sex and intimate relationships, prematurely. It is different from assault, harassment, & rape.
In 1919, Marxist theorist Georg Lukacs of Hungary enacted a radical sexual education where children would be eroticized and taught to be promiscuous. That is, institutional care was configured such that children would be taught to view the Self by another, novel metric [to them] -- sexual value.
The Marxists observed that sexual promiscuity education for children at young ages destabilized them. Furthermore, they noticed that this destabilization worked in their favor. Destabilizing children and the early loss of innocence results in the destruction of the family unit. Destabilized children tend to stray from the authority of their parents and often turn to the state or other institutions for parenting needs.
Under normal conditions, a healthy 8 year old is unaware of sexual value. That is, the 8 year old does not view the Self as potentially sexy. If through persuasion, the 8 year old can be convinced of this hidden dynamic among and between people, then the 8 year old has been over-sexualized, and becomes aware of the potential for others -- including adults -- to view him/her as sexy or erotic. The 8 year old becomes a participant and competitor on the sexual/relationship market. Upon viewing adults as competitors, and subsequently peers, the child begins to stray from the authority of his/her parents, and is more susceptible to whosoever comprises the institutions.