Back in the heyday of “blaxploitation” cinema, the men were men — laws unto themselves, righting social, racial and criminal wrongs with their fists and guns.

Women were, well, objects of desire — conquests, helpless in the smouldering gaze of our heroes. Or shrill resisters of those charms.

And heaven help the young guy whose eagerness to join in on those “conquests” wasn’t, shall we say, obvious.

Whatever else this latest, jokey reboot of “Shaft” is, at least the screenwriters got that retrograde sexism and Afro-American homophobia right.

“Ride Along” and “Think Like a Man” director Tim Story and his screenwriters struggle to update Shaft for modern tolerances, finding nervous laughs every time the “Black James Bond” (Samuel L. Jackson) questions his F.B.I. analyst son’s sexual preference. “Besmirching our family name” is one way Dad describes it.

And they strain mightily for laughs in this long, body-strewn action comedy.

Not that there aren’t plenty. But when you rely on every time Samuel L. drops the “n” word or his many colorful variations of the F-bomb to get a giggle, even that wears thin after a while.

The comedy in this convoluted hunt-for-a-murderer-mystery revolves around the contrast between Junior (Jessie T. Usher, of “Independence Day: Resurgence” and TV’s “Survivor’s Remorse”), a buttoned down “metrosexual” in sneakers meant for “badminton,” and his ’70s-80s badass private eye Dad, who still busts heads, pulls triggers, drives a ’71 Chevelle SS and wears way too much leather.

John Shaft Jr.’s ex-junky college pal (Avan Jogia) has died under mysterious circumstances, and Mr. “I hate guns” figures he can stop data digging long enough to figure out who did it by working the streets.

Getting slapped around is getting off lightly with those folks.

So, behind his sure-to-disapprove mama’s (Regina Hall) back, Junior seeks the help of his estranged, absentee Dad (Jackson).

Junior is about following the digital trail, Dad is about going out to “baby sit your ass” while they “handle our bidness.”

The kid is smart-phoned to the max. Dad keeps his files as…files — scattered all over the office where he occasionally beds a comely client.

As this case involves an Army vet and onetime drug addict who also happened to be Muslim and attended a New York mosque on the F.B.I.’s watch list, it will require delicacy, diplomacy, not going off half-cocked.

John Shaft is none of those, especially — to hear him tell it — the half you-know-what.

As the duo picks, punches and pistols their way through New York, Shaft Senior is all about schooling, or least insulting through innuendo, the “fluid, cis-gender” coconut water-drinking, hip-hop loving kid who bears his name.

“Women want a man to be a man…Men don’t APOLOGIZE.” And about those clothes, your “tight-ass jeans’r cutting off the blood to your BRAIN.”

Junior comes to realize, to his dismay, that “There’s NO non-violent people in Harlem!” And that Dad’s “Give her the Shaft, boy!  It’s your duty to please that booty!” isn’t going to work on his college crush, Sasha (Alexandra Shipp of “X-Men:Dark Phoenix”).

She hates the kid’s sexist, racist, homophobic and trigger-happy old man.

So, too, does Dad’s ex, Junior’s mom.

Until, of course, she sees him back in action, her eyes lighting up at his masculinity and mad firearm skillz.

Sadly, as the bodies pile up, Sasha too gets that turned-on-by-gunplay look in her eyes. If you ever doubted guns were penis substitutes, “Shaft” settles that. It’s a shame the filmmakers thought being glib about gunplay, flippant about firearms, is funny in itself.

It’s one thing to bring back the leather, the muscle cars and the turtle necks. It’s quite another to revive stereotypes for cheap laughs or glorify guns as a symbol of manhood.

Laughs of every kind become harder to come by the deeper this “Shaft” goes down the um, rabbit hole. The missing-from-the-movie villain (Isaach De Bankolé) is a non-entity, young Usher underplays John Jr. to such a degree that he’s rarely funny enough to warrant watching.

And the original Shaft, Richard Roundtree — you’ve seen the TV commercials, so this isn’t a “spoiler” — doesn’t show up early enough to save the comic day. That leaves Jackson to carry the picture, even he’s a little tentative with some of the attitudes he’s espousing and lines he’s trying to finesse.

I appreciate the direction they wanted to take this, but the jokes needed work, the ridicule should be more directed at Jackson’s character’s various blind spots and intolerances — “This is my ‘Puerto Ricans I don’t trust’ file.” —  and disrespect for human rights.

At some point, too, gun worship becomes fetishized. Story didn’t make those moments of mayhem, or choosing which firearms to make that mayhem with, amusingly over-the-top. They’re just violently over-the-top.

That pretty much goes for the movie as well. And that’s more an ’80s “action comedy” thing than a “Shaft” tribute. Ya dig?

It’s MPAA Rating: R for pervasive language, violence, sexual content, some drug material and brief nudity

Cast: Samuel L. Jackson, Jessie T. Usher, Regina Hall, Alexandra Shipp, Isaach De Bankolé and Richard Roundtree

Credits: Directed by Tim Story, script by Kenya Barris, Alex Barnow, based on the character from the Ernest Tidyman novel and 1970s movies. A Warner Brothers release.

Running time: 1:51