By rating given, are you speaking of the score that this website would give it? I have never personally written a review, so I cannot say for sure, but having played the Witcher 2 (and LOVING it but also being APPALLED at the content) I would have to say that it would score very low.
The sexual content is very graphic (read: horrendous); I was very disappointed with that aspect and it has kept me from playing through the game again.
The violence is pretty rough, too, but I've seen much much worse and didn't find it too troubling (for me, at least).
The language was worst in the first game, in my opinion, but it's still pretty harsh here. Just about every word in the book is used, not only in sequences of dialogue, but also from the random chatter found throughout the cities.
I hope you find this helpful. Technically, The Witcher 2 is a masterpiece of gaming wonder. "Morally," it's a mess.