Why not? The twist itself isn't that dark for Hollywood.
And it's not like there was a lot of the sex shown in the original too so Hollywood doesn't even need to be worried about that part either.
Not dark? The father learns that he ****ed his daughter. The daughter is being held captive, with the evidence of their incest just in arms reach. The father, not wanting to harm the innocence of the daughter, cuts his tongue out, then has himself hypnotised so that he wont even know it's his daughter, and continues to live with her as a lover......
Not only that, but the raw emotion in that scene is just as epic as it can get. You get to see this guy, who went from being a drunk to being a bad ass, just grovel at the feet of the man he wanted vengence on. You see him twist in pain and emotional agony, and the roller coaster of highs and lows.
Honestly, I haven't seen an American movie that has put that kind of feeling in me. Choi Min-Sik is one of the best actors of this time. All the movies he acts in, are just excellent.