On the Laws of Deuteronomy

Lent started this week. This is the first year I haven't given up something (because my health and fitness goals are actually being accomplished); instead, I'm taking on increased study of the Bible and Christianity in general. So I'm reading the Bible straight through. Or, rather, picking up where I left off in the Bible last year.
As I was searching for my page, I came across an interesting law in Deuteronomy. The passage caught my eye because it raises a very relevant question when reading Deuteronomy: "WHO DECIDED THERE NEEDED TO BE A RULE FOR THIS?" Obviously, it was a problem, or nobody would bother writing it down, right?

The rule is from Deuteronomy 25:11-12:
"(11) If men get into a fight with one another, and the wife of one intervenes to rescue her husband from the grip of his opponent by reaching out and seizing his genitals, (12) you shall cut off her hand; show no pity."

This passage is interesting because it demonstrates the highly gendered society that existed in the Biblical era. Instead of addressing the reason the men are fighting, the law concerns cutting off the hand of the woman who tried to distract her husband's opponent. What problem are the Deuteronomy writers trying to solve with this? Who will be helped by this woman losing her hand? Instead of having two people with black eyes and one person with sore genitals, there is an ADDITIONAL injury in the woman who now has only one hand.
Obviously, there was something about this situation that people of the Biblical era had a problem with - most directly, the fact that a woman is touching anyone's crotch, and especially that she has to touch the crotch of a man who is not her husband. Is this some sort of rendition of coveting someone else's spouse?
It can't be - the text specifically says that the woman is reaching out "to rescue her husband from the grip of his opponent." To me, her tactic seems to be a clever idea. From what I understand, mens' genitals are very sensitive, so it would seem like a good idea to distract him by grabbing at his most sensitive area. The wife is not grabbing this man's crotch in any way EXCEPT to distract him from hurting her husband. And yet the woman is the one whose hand will be cut off. Why is this?
Does anyone know?