William Friedkin’s NC-17 rated “Killer Joe” was given a killer screening July 23 at the Tribeca Grand Hotel in Gotham.

“It’s almost my third NC-17,” Gina Gershon noted at the No. 8 afterparty. “They almost had ‘Bound’ as NC-17 but they changed it at the last second to avoid the rating.” Of course, “Showgirls” is the thesp’s other definite NC-17.

“‘Killer Joe’ has always been a bit of a lightning rod,” said playwright-screenwriter Tracy Letts. “Even when I was doing readings in the early days, I would be applauded and assaulted by the audience at the end of the night.”

Matthew McConaughey, riding a career wave he dubbed “McConnaissance” with five new films and an HBO series, noted that he skipped frontal nudity. “It’s not NC-17 because of why I’m a man. No,” he said.

“I think Matthew was willing to do the full monty,” Letts added, “but Billy was careful because he was trying to avoid an NC-17 rating. And I told Billy, ‘You’re crazy! We’re not going to get an NC-17 rating.’ Shows you what I know.”

Friedkin had the final word on the LD Entertainment pic: “They gave the right rating. I’m too old to lie about this stuff and cut the film back by less than a minute or two to get an R. Who cares who’s naked? It’s not important. It’s not about nudity or violence. It’s about people who are trapped by their own dreams.”