“The Nice Guys,” writer-director Shane Black’s darkly entertaining R-rated homage to action movies of the 1970s, is not particularly nice. But it’s a whole lot nicer than many of the films that inspired it.

Low-rent L.A. private eye Holland March (Ryan Gosling, displaying admirable physical comedy chops) is a drunk and a screw-up, but he knows it. He stays just sober enough to care for his smarter-than-he-is 13-year-old daughter Holly (a terrific Angourie Rice). He willfully takes money from clients he should not – like the dotty old woman whose husband he agrees to find, even after noticing the man’s ashes in an urn over the fireplace. But he generally tries to steer clear of violence, and is constantly surprised when it breaks out around him.

He’s also remarkably quick to forgive.

When a strong-arm for hire named Jackson Healey (Russell Crowe, effectively underplaying) breaks the hapless PI’s arm to discourage him from searching further for a missing girl March has been hired to find, it isn’t long before the two scruffy misfits have teamed up together to find her.

It’s the missing girl (Margaret Qualley), it turns out, who originally hired Healey to scare away March, believing the PI to be one of the trained killers who’ve been on her trail. It’s something to do with an X-rated movie she recently made, one with an anti-automotive message, which has apparently put her in the sites bad guys representing Detroit, the L.A. porn industry, and possibly the U.S. government.

The bad guys on her trail are seriously bad and flamboyantly villainous, especially Keith David as the stylish, leisure-suiter Older Guy, and Beau Knapp as the scarily demented Blueface. Then there’s John Boy (Matt Bomer), so named for a certain physical resemblance to Richard Thompson of “The Waltons.” All three play their part like it’s an audition for a remake of “Baretta” or “The Rockford Files.”

Crowe’s affable Healey, for his part, is a different kind of thug. A good-natured brute who hates bullies, he will rough up pretty much anyone for money, but prefers hurting those who abuse or threaten women and children. He’s the kind of guy who hurts people quickly – it’s just a job, right? – and then gives them helpful medical advice, all while warning them to shape up and be better people.

Crowe is delightful, and he and Gosling make a great team. Some of the best moments of the film are the loopy moral debates and negotiations they frequently engage in, usually at inopportune moments. One such conversation takes place early on, in a public restroom. It’s hard to say which is funnier, Gosling’s attempt to brandish a gun while keeping the stall door open and covering his privates with a magazine, or Crowe’s calm, patient expression as he watches the man on the toilet try to act like a tough guy.

From its gleefully frivolous approach to violence, to its main characters’ malleable sense of right and wrong, from its appealingly off-the-cuff, almost improvisational sense of plotting, to its earnest inclusion of a timely anti-establishment social message, Black’s goofball lovefest of a script strongly suggests that the author was more than just inspired by the morally ambiguous, B-grade shoot-em-ups on which audiences thrived 40-plus years ago.

Shane Black clearly loves them.