The lesson exists even without the novel interpretation that a strand became entangled.

Noam, it's worth giving some credit and thinking a bit before launching a blunt attack. Rabbi Yitzhak's suggestion explains the event well, even if it has an aggadic element to it.
In the verses it says that immediately after the rape, Amnon's attitude flipped from love to hatred. So something that happened during the rape caused two things: (a) the end of the love, (b) the birth of hatred.
Rabbi Yitzhak explains that Amnon's "love" depended on his lust. So if the love ceased, apparently the lust ceased too. Why did the lust cease after the act? Because Amnon became one with a severed urethra, and that apparently diminishes lust. But it's still difficult: even if lust ceased and love ceased, why was hatred born? To that Rabbi Yitzhak explains that she did something that hurt him. Her resistance before the act is not the point, because the fact is that Amnon wanted her and acted despite the resistance, and after the act suddenly he no longer wanted anything. And what could she do during the event? She tied a strand around him. That's one thing Tamar could do during the act itself, and it would cause both a reduction in lust and the birth of hatred.
Maybe other psychological explanations can be suggested for Amnon's feelings, but this explanation is completely reasonable (and it appears in the Maharsha there).

Rabbi Michi, the Talmud there avoids the psychological idea that the offender hates the victim and instead looks for deliberate direct harm: "A strand became entangled around him and made him one with a severed urethra. But if it became entangled around him, what did she do? Rather say: she tied a strand around him and made him…"

By the way, maybe this matter of the severed urethra also comes to explain, from the standpoint of Jewish law, why Amnon sent Tamar away after the act (and in her eyes the sending away was "this wrong in sending me away is greater than the other that you did to me"). And Rabbi Yitzhak explains that Amnon knew David would not give him Tamar, because one with a severed urethra is disqualified from entering the congregation. So his lusts were nullified, and all that remained was hatred because she prevented him and injured him, etc. [The Talmud there also explains how Tamar could even suggest to Amnon that he ask David's permission, seeing as she was his sister, and answers that Tamar was the daughter of a beautiful captive woman and had converted.] So Rabbi Yitzhak's whole interpretation is indeed a bit aggadic, but it has internal logic.

With God's help, eve of the new month of Elul, 5781

Tamar was a brave young woman. She not only pleads, "And I—where could I carry my shame?" but also threatens: "And you will be like one of the scoundrels in Israel." I will not stay silent, but will publicize to everyone what you did, and your name will be denounced in infamy as "one of the scoundrels in Israel."

After satisfying his lust, Amnon realized that he had "ended his career," and from now on would bear the disgrace of a scoundrel. If he took her as a wife, everyone would understand what had happened; and if he sent her away, she might carry out her threat and publicize his disgrace in public.

And she did indeed carry out the threat: she put ashes on her head, tore her garments, and "went on her way, crying aloud." After such a "demonstration," Amnon's public standing was no higher than that of one with a severed urethra. Amnon lost any chance of "entering the congregation of the Lord." No self-respecting family would give its daughter to such a man.

And it may be that this brave young woman, who did not "keep the trauma bottled up" but immediately made her cry heard in public, also taught the rapist a lesson through painful physical injury and made him "one with a severed urethra." Scripture taught, and the Sages taught, the daughters of Israel not to suffer in silence, but to teach the rapist a painful and deterring lesson.

Regards, Amityoz Yaron Shenitzlar

The date:
28 Av 5781

(Eve of the new month of Elul will be on Sabbath, and I'm not one of those "religious people who text" 🙂

I meant that the offender hates her for defending herself, even though it was legitimate. Like the urban legend about the burglar who was injured by the glass shards the homeowner placed at the bottom of the window when he broke into the house through that window, and then sued the homeowner.

An urban legend? Meaning it's obvious to you that morally he's allowed to put glass there. Like your incomprehensible view that in order to stand on "my right" to my property, it's permissible to kill some stubborn person who insists on stealing. And in the end this stems from a strong attachment to categorical imperatives.
Now I think I've understood a point. Tell me if I got it right. In your view, morality is an obligation that really truly must be carried out in practice, and in your opinion people are usually moral. In my view, by contrast, "morality" is demanding in an inhuman way, because it looks down from above on everyone and gives no priority to anyone. For example, if a great king tells me, "Hold out your hand to be cut off, or I will cut off So-and-so's hand and also give him a pinch," "morality" solemnly obligates me to hold out my hand. Likewise it commands me to share all my "property" with whoever needs it more than I do. But that's too hard, so people don't do it and dismiss it as they always do. For you—correct me if I'm wrong—it comes out that morality does not demand things that a reasonable person cannot live up to.

An urban legend because it's doubtful that it really happened. But yes, in my opinion it's obvious that it's permissible to put glass there.
I don't know how you arrived at that implication of the disagreement between us. I think the main disagreement is that you're a consequentialist, and so in the case of the hand you say what you say. To me it's obvious that although your outcome is better, I have the right not to give my hand. A person is allowed to give himself priority in his own action (your life takes precedence).

Do you have any moral demand that is very, very, very hard to realize? Or do the demands fit ordinary conduct that, all in all, doesn't outrage instinctive feeling? And if they do fit, is that just luck, or is there some essential reason? (I offered a far-fetched hypothesis about what underlies opposition to consequentialism, because unfortunately it's genuinely hard for me to understand how one can oppose it.)

In this particular case I can present my position as a different kind of consequentialism. The weighted outcome, where the weight of consequences for me is greater (because this is my act and my decision). I don't accept the veil of ignorance when the decision is mine. Not because it's hard for me to conduct myself that way, but because it's not correct.

When I'm told to kill someone or die, the correct decision is to die ("who says your blood is redder?"). That's a very hard decision.

I understand. But that's a hard decision that comes up once in an unimaginably vast number of generations. In day-to-day life there's no gap between the demands of morality and normal behavior, and it's just luck that humanity got so lucky. (In my opinion there are huge gaps. And to preserve one's sanity, one has to settle for being only "traditional.")

By the way, in my opinion the correct decision is to kill and not to die ("who says your blood is redder?"). One is permitted to die, one is permitted to kill, and you're not even obligated to draw lots. But we've already chewed this over.