NC-17 in the U.S. is what used to be called x-rated. Nobody under 18 is allowed to see it, period. And a majority U.S. theatre chains will not show NC-17 films, period, so the rating is often considered a kiss of death for a movie (the studios won’t spend money marketing them). So, as this film says, any gay sexuality (without nudity, as the film shows), or sex where the woman is enjoying it, or anything other than the missionary position = NC-17. And there are no precedents (they don’t compare to other films they’ve rated previously, so some r-rated movies seem raunchier than NC-17/X-rated ones, ex. American Pie, Scary Movie) or formulas – it’s entirely based on what makes the panel members uncomfortable.

R is a “better” rating. Under-18s can get in with an adult.

I’ll quote the last paragraph:

You have to wonder what kind of values are being advocated when people losing body parts and being killed in the most ghastly ways is completely acceptable for general audiences but seeing two people express love and affection for each other is a grave sin from which we must protect the next generation. Only one question remains, I guess: what is going to protect me from the kind of generation that grows up on such values?