"I wrote imprecisely in saying he "clearly raped a young girl". I meant that if we had been there watching we would have known that -- not that when we're hearing the story later it is entirely clear."
Yep I got that and I think we mean the same thing. If it is in some way clear for example by two people watching it, it would be obvious to them and the trial would become easier. Having other people be a part of the experience can be fun and also increases true consent and decreases chances of losing control.
"I suggest that the benefit of protecting underage girls from rape when evidence is weak is more important than deterring desired relationships."
But you are suggesting that increased importance regardless of AOC efficacy so that if many more desirable interactions are deterred compared to the degree to which underage girls are protected from rape, you would still assert that increased importance. That's literally ir-ratio-nal because it ignores the ratio of bad/good prevented.
"Would they really completely understand that the relationship is temporary? I don't think most girls are wired that way (the landscape does look on average quite different for gay young-teen boys)."
Every child and person is unique and we educate our young ones in understanding that many things are temporary and have been doing so for a long time. It makes sense for children to learn this especially in today's quickly changing social environments. So yes they would understand that much more than in earlier times, definitely much more than when the AOC was increased in the 19th century.
"Also, look at what IS allowed: they can have non-sexual friendships and flirtations with older people. They can experiment sexually with their peers. You agree they probably shouldn't be thinking long-term. So what they give up is short-term sexual relationships with older people? This benefit is looking awfully slim in application and importance."
Yes, the law allows it. But in practice many of these interactions which are allowed are deterred by the social situation which emerges from the AOC law. Combine 140 years of increased AOC with a media which likes to expose every person of a country to the worst events that have recently occurred; what arises is a systemic sexual repression due to the pathological association between youth, sex, and violence, which leads to systemic social oppression. Besides the sexual interaction is by far the most powerful and beneficial expression of love from which point of view it appears as a mistake to block that.
"Different case! I specified that the woman was convinced the man was going to marry her, based on his promise. She felt no need to use sex to get anything. The woman presumably simply had sex with a man she thinks is about to marry her because she expects they both will enjoy it."
You did not specify that apart from being convinced the man was going to marry her, the woman did not also see the sex as a way to further consolidate that future. In any case the point behind that example was that in a sexual interaction the time where consent and evaluation is most important is before, during and shortly after the interaction. You can attach another different value evaluation some time afterward but this will decrease in importance relative to the initial evaluation given its proximity to the event evaluated.
"The false promise might be not ideal, but when he takes action which he knows people very commonly view as restricted to committed relationships, that's when it gets much worse."
Or maybe after the sex the man realized it was so good that maybe he will indeed marry the woman. The point is, when you invoke future effects and evaluations of some event, it can go in any direction. Some of the most happy and successful people are the ones who have suffered the most earlier on. That is not to say that suffering is good, it's just to say that a single event can be evaluated in its approximately original form (i.e., viscerally) immediately after the event, before its distortion gradually decreases the accuracy of its evaluation.
"We haven't defined just what "bad" means here."
Actually we have, the definition of a bad interaction is one for which one of the two people of the interaction evaluate the interaction as bad.
Also, "bad" is the word people use to describe those events which they'd want to experience with a lower preference than all the "good" ones.
"The law allows for children's view of things that happened to them changing as they grow up, and even expects it."
But that change is to some extent formed by society which to some extent is formed by its laws, and so obviously when an underage girl after having had sex with an older person realizes she did something illegal, she will receive negativity from the society which she will probably project on the person she had sex with. Hopefully their relationship will have been a good one so they can overcome that. AOC to some extent is contributing negatively to socio-sexual health.
"Consider a man who offers a 4-year-old a shiny dime in exchange for a ratty-looking twenty-dollar bill. The child can at the time genuinely desire this exchange, but we expect that they will come to feel they were wronged within a few years. If an adult accepts the dime-for-a-twenty exchange, that's entirely their business."
But why do you expect that they will come to feel they were wronged within a few years? It seems like an entirely sterile economical type of reasoning which has nothing to do with an actual situation. You are suggesting a social encounter of some sort within which some form of trade is made. I'm assuming that the social part of the situation is positvie. The long term effect of having been scammed for 20 dollars will be a lesson to the child, it doesn't make sense that the child in the long term still feels bad about such a small thing. In the end it will just be a story. If that is negative for the child, something has gone wrong in its processing of the event. Traumas such as the one you describe should not latch on like that, so if the child still suffers from such an event then the child needs some form of extra care to deal with the general problem, regardless of that specific exchange in which it lost 20 dollars. This is important because when education and upbringing go right, microtrauma is quickly overcome. In that way we can actually expect good evaluations of past events which have had immediate negative evaluations, simply due to the learning effect.
"I'm not arguing for any particular age of consent. Obviously it's tricky and God never said it's got to be 16 or 18 (or 14). I say leave it up to the teleios (ordinary folks) to sort it out."
I'd argue for 12 given that's where it was for a long time until about 140 years ago. Physiologically puberty starts around 12 so it just seems obvious to align it and of course punish rape higher when a younger person is involved. It doesn't make sense for the teleios to figure it out without the ones it concerns because they don't see how it benefits them.