The similarities between a fetish and a PTSD symptom are not small since both derive from trauma, the major difference being that women don't develop fetishes. A trauma occurs when the stress that the mind experiences is too great for it to tolerate and a symptom, which is the indicator that something is wrong and change is needed, is created.
But first a story. A teenage boy was crippled by his fetish of staring at and photographing women's shoes. Fetish derive from early life trauma during which a young boy, having witnessed a naked girl or his parents' sexual activity, illogically fears that he may lose his penis since the female lacks one. Thereafter, to reassure himself, he compulsively touched or viewed the object symbolizing his penis (with him a female's shoe) for reassurance that he still had it. I advised him that, when the obsession arose, to talk to himself: tell himself that while the obsessive thought had helped him in the past and he would always be grateful, he no longer needed its help. That both could now relax and would always be friends. Within two months the fetish disappeared as our discussion turned to the normal teenage concerns of dating and future vocation.
Similarly, a soldier who survived combat may, for decades thereafter, experience crippling anxiety when encountering something reminding him of his wartime experience: a battle scene photograph or video or reading of such incident. Relating as did this boy to a soldier's distress may prove helpful: telling himself that the symptom, which was intended to save his life during combat, was no longer needed and could relax but they would always be friends.
While the unconscious can protect against distress it is primitive, illogical, ever-vigilant and powerful, but lacks a sense of time.