Tom O'Carroll and Dissident are willing to include in their evaluation of Margaux's sexual relationship with Peter that given her miserable home life, she might have been better off with the relationship with Peter than not having it. I think (and Margaux herself thought) that might be true -- but sometimes consequentialism fails.
Suppose a 6-year-old girl in the Third World is dying of a disease that is curable in the West. A man offers to take her to America and cure her if she will become his until the age of (say) 18. So the family and the girl reluctantly agree.
The man feeds her and clothes her well, sends her to school, and lets her play with lots of playmates, and go on fun vacations. He listens to her and loves her like a father and plays with her.
The one catch is his particular sexual fetish. He gets sexual pleasure from slicing off her left leg a little at a time (under anesthesia, so no pain involved). And so he does... her left leg gets shorter and shorter as the years pass.
Surely she's better off than if she was left to die in the Third World. People with only one leg can have pretty good lives. And yet... I suspect (and hope) most of you would join me in saying, "No! That's not right!"
Surely she'd be even better off if the man didn't remove her left leg, but then he's not a saint and he'd only take her on the condition he could get his needs met in that way.
So, for the parallel? You will naturally object that some young girls love sex. I think it's very few, but in any case it's certainly not Margaux in relation to Peter, and that's the case we're considering.
Early on in their friendship, Peter has convinced Margaux to play naked in the basement, and she sits astride his motorcycle. He turns it on and she has an orgasm. It's of great interest that she never once mentions asking to do that again, nor does she mention him suggesting it. She's had peak sexual pleasure, but has no desire to repeat it. Sometimes context matters a lot.
Sexual activity with Peter is entirely for his sake, and she does it grudgingly. If she occasionally insists on it later and uses it as a weapon, it's part of a power play, not what sex is supposed to be.
Did her unwanted sexual relationship with Peter affect her?
...myself later giving the blowjob and something in me: a flame of some sort just dying and perhaps never to be recovered ... Later on in my teens and twenties what happened between Peter and I in the basement greatly affected my ability to desire sex and it was only after heavy therapy (EMDR in particular) to address the abuse, that I was able to desire sex. I missed out on desire it for a good portion of my twenties and really disliked it and did it only to please a man and got involved with males that sometimes capitalized on this or abused me further.
Even in a society where adult-child sex was approved, last I knew none of us are suggesting kids do something they don't want as a quid pro quo.
If you think removal of a leg is surely more traumatic than unwanted sex... I think that's presumptuous of you. We know that psychological abuse can be more damaging than physical abuse.
Perhaps we think that Peter thought Margaux genuinely wanted the sex and was just mistaken. You might be right -- and this feeds right into why it's good that adult-child sex is illegal. Another quote from Margaux:
One thing that happened that's not in my book: there was a four-year-old present in Peter's life when I was twelve. I'll call her Joan.
Well, Peter began to molest Joan and Joan came to me to ask me to talk to Peter and explain that she didn't like it and didn't want to do it anymore. Peter actually became mad at me for telling him this, but then he did stop with Joan -- I think he could no longer rationalize the behavoir to himself after the Joan incident.
So if you want to think of Peter as not so bad because Margaux might have been worse off without it, compare it to your evaluation of my leg-remover man. Keep in mind that many pedophile men cannot be trusted to figure out whether consent is genuine. Maybe the girl who loses her leg consents too, since the guy has been so nice to her and saved her life.