This seems to work especially well with women: whatever male has the most attention becomes the most desired male, whatever woman has the most attention because who women most want to copy.
Men generally have a more direct sex appeal : do this or you will be shunned by women (or insignificant, weak).
Fundamentally, what does it demonstrate - more than mental manipulation? It demonstrates where humans place their meaning in life. Allegiance and subversion to secular values. Foolishly thinking they are rebelling against all authority and making free choice, they instead find their choices made and enforced for them via secular means. Renouncing good, they have no means by which to judge good but for what constant propaganda influences place upon them.
This is similar to the mechanisms of cults: all outside contact and authority is broken, all social contact is limited to other members and all authority placed upon the leader. In this case, we find the cult has become "mainstream", nevertheless we see its truth in the general harm and evil it causes. Of course, it claims this evil is good, because having broken contact with God (and even nature) the "individuals" no longer have a means to judge good.
From a Christian perspective, one would see a parallel to Satan. Satan having rebelled against God falls and creates evil. Here, those who rebel against God and traditional values find their values replace by Satan's and their will directed towards evil. They are not free, but merely demonstrating their submission and slavery to evil.
At its simplest, a person who follows every fashion wherever it leads, or a person who has face and body carved into that of a younger or different person, or a person who marks or mutilates himself and displays the result with pride... such a person is advertising their subordination to secular values.