I think also it can be difficult to know if the woman give consent
No it's not. If you have questions around the woman giving you consent, then you should check.
re Bowdon's post: That last part is probably what happened, I've heard of that happening before in a uni, one guy gets the girl to consent and then the others wait outside and essentially ambush the girl.
No doubt the video shows her having consensual sex with the one guy, which she probably regrets.
"Essentially ambush"? No, that's rape. Gang rape at that.