HOW KINKY IS THE SEX? Don’t let the R rating fool you: It’s pretty kinky. There’s whipping, flogging, hanging from ceiling hooks; there’s talk of anal and vaginal fisting, though neither actually happens (Ana strikes them from the contract). But here’s the problem with the sex in the movie: It’s not sexy. And that’s not because I’m not personally into Red-Room-level BDSM (occasional spanking and hair-pulling only, please). It’s because Christian and Ana’s relationship isn’t much of…