This is not a marginal issue. Ever since the beginning of antis, back in the 1850s or 1860s, your main tactic has been to lie. Every statement which has been independently tested has come out to be a pure lie. Not even an ambiguity or a provisional truth which hadn't been refined enough. No, an outright lie invented because it would constitute an argument if believed. You antis are an empire of lies. And the direct way to prevent your expansion is to question everything you say. You do not have room to negotiate anything. You have been lying for 150+ years, so everything you say has to be taken as a lie until proven true.

You are right. It is hard (although not as hard as you say and has been done alreaady) to establish whether harm is iatrogenic or not. But it is hard to establish whether harm exists or not. Post-sexual trauma is a language game where therapist and victim both are assuming specific game roles and defining themselves through them. So post-sexual trauma has the important features of hysteria -- which is recognized now to be a product of society more than it was a real illness; which is not to deny that hysterics did feel the symptoms they presented. But same as the existence of hysteria is dependant on the society which interpreted a set of roles in games played with some symptoms presented as hysteria, the existence of post-sexual trauma is also dependant on a society which creates those roles featuring certain symptoms. So if iatrogenic harm is hard to prove, all harm is hard to prove. Victim is a social role too and as such is also an expectation placed upon people.

Further, very few people has ever posited any causality; and those who have, have only advanced very tentative hypotheses. In the case of post-sexual trauma, there is a large problem. There are many other variables intervening. Not just therapy or social opinions. In the intervening years between a consensual sexual experience and its reclassification as harmful, there could have been and maybe were, many other experiences which could have been traumatic to the child, both discrete events (say, an accident) and long term states (say, parental divorce.) The time of the consensual sexual experiences isn't even really all that relevant, as there could have been other traumatic events or states prior to the sexual experience or overall simultaneous to when it was happening. But since sex is considered different and unique, all therapists, all external observers, and probably most of the victims too, blame the sex and assign any causality for present-day problems in living to it.

We see the opposite with boy circumcision. Adult men go to the doctor because of problems with erections. The doctor asks questions, and attributes the erectile dysfunction to diet, lack of sleep, alcohol or tobacco, general stress. It is never attributed to circumcision because circumcision is regarded as normal. Sure enough all of the other physiological or psychological factors have an influence in erectile capacity, but the lack of a foreskin is a greater factor which is not even mentioned because it is also considered different and unique -- albeit for its lack of importance, rather than the reverse.

I bet that if the doctor found out about both circumcision and early consensual sexual experiences, he'd blame the erectile dysfunction on the latter rather than the former. And probably so would the victim.

But the hypothesis of iatrogenic harm is pretty simple. If at t=0 you don't feel harmed by an event which is happening at the time, but after its termination or the end of its recurrence, at t=1, you do, then whatever makes you feel harmed did not happen at t=0 but between t=0 and t=1. The fact that many children do not feel harmed at t=0, so much so that even anti literature has to devote lots of space to them and to the techniques to make them feel harmed, is enough to prove this.

Even without bringing in history and anthropology, which really have already solved the debate once and for all and without question.