What occurred wasn't illegal, just immoral and sickening
So Stallone and his then bodyguard are accused of having sex with a 16 year old. 16 is the age of consent in Nevada. She took a key and went to his room (consent).
Stallone fooled around with her (half sticking it in) before calling out his buddy. He asked her if she'd had sex with two guys before. She didn't protest. She didn't run from the room. She then performed oral sex on both of them.
They then joked that if she told anyone they'd have to smash her head in (yeah real funny isn't it?)
She left feeling really dirty. Who wouldn't? 16 and just had sex with a 40 year old and his bodyguard, before being threatened.
The threat could be a crime, but because they laughed, could be excused a bad joke.
The sad thing is that all of this began with a child meeting another child in the video arcade, the actor who played Stallones son. It sound so innocent. Family on holiday, meeting other kids and thinking you could meet a star. Sickening. But that's what stars do. They use your fandom to their advantage.
I'm expecting an avalanche now, and given that Stallone at 40 would get with 16 year old (and he was a dad himself back then) shows that he has a thing for young girls.