Why do girls laugh when they see really serious, brutal nut-shots, where the guy might be permanently damaged, even when the guy is their friend?

I've seen some of these videos, or reaction videos to it, and if there is a girl present, she often breaks out into hysterical laughter - same goes for girls reacting to the video.
Guys might laugh too, but it's more like a nervous "holy fucking shit" laughter, while the girls just enjoy the fact that a male's male parts got brutalized, and that he's in male pain and humiliation.

I've seen videos where a girl watches their male "friend", and lands with his entire body weight and high speed on a metal railing or the edge of a pool, and crushes his balls between it and his body, and the girl who watches just finds it hysterical, before even knowing he's fine.

Why? What the fuck? And what is wrong with girls who are amused by the idea of a guy's testicles being destroyed or cut off?
How is that better than if a guy enjoyed the idea of a girl getting fucked with a knife?
Why do girls laugh when they see really serious, brutal nut-shots, where the guy might be permanently damaged, even when the guy is their friend?
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