The claim is not that it would be toxic, but there is a significant risk of bad outcomes.

Which is exactly what happens when you imbibe a toxic substance, real or metaphorical... there is a good chance you will get sick.

We agree there is a significant chance of bad outcomes, but where we differ is that I argue in concert with the evidence--that the bad outcomes are significant because of the current laws and attitudes--whereas you argue in terms of belief, assumptions, and moralism--that the bad outcomes are likely for reasons that are somehow fixed in nature.

This harm is not inherent to the activity itself in the moment or to the intention of the pedophile -- but I think it highly likely that it's not all arbitrary social convention either. I fear it is inherent to innate long-term patterns of feelings among many girls -- at least a significant minority.

And you have no proof of this, but go by a common sentimental, moralistic belief of female fragility, only transposed onto particularly younger females in this case. And your suggested solution is total prohibition rather than education, support, and guidance, which reeks of a draconian solution to a largely moral issue.

You could claim that a person cannot feel good about sadistic fantasies because harm to another is inherent in full expression of the desire. (You could also argue that there is no need to feel bad in that case either, but let's leave that aside.) And many antis express the view that pedophilia is exactly like that -- but I certainly don't. Since the risk of harm is removed from the act, it need not affect self-concept. (This assumes a situation that is ideal in other respects -- situations that we would both agree are harmful abuse do occur.)

Suppose I really want to have intercourse with a grown woman, who reciprocates those feelings. Suppose I the find out (but she doesn't) that this will make her very sick. I have no need to suddenly feel guilty about my desire for intercourse -- all I have to do is abstain from the activity. The parallel is not perfect (it never is) but it shares this aspect that the risk of harm is removed from the activity.

Why would this woman get sick? How would you know if she wouldn't? Again, I suspect this is based on an assumption arbitrarily formulated based on her gender, and not on the basis of any substantive, tangible concern that could be clarified scientifically. Maybe her "sickness" is the ruination of your chaste perception of her more than anything else, and you project this as her problem rather than yours.

What I am trying to explain here is a rather specific point: how one can feel good about pedophilic desires but also feel they can never be acted upon even if society changes.

Yes, I get what you mean, but that amounts to a personal moral conviction you have, very analogous to the idea that pre-marital sex should be refrained from even if it's legal, or society ceases to condemn it any longer. It doesn't amount to a concern for harm in any empirical or scientifically valid sense. This is why I emphasize the separation of fact and belief, just as I support separation of church and the law-making apparatus of state.