Stupidity isn’t a virtue, but it can be amusing, sometimes even endearing. How else to explain my fondness for “Red 2,” an action comedy delivering dumb fun by the ton? It’s utter drivel coasting by on slick proficiency (at 100 miles an hour).

As anyone who saw this film’s 2010 predecessor knows, the bar of expectation here hasn’t been raised above sixth-grade height. This is simply a planes-pistols-and-passports time-killer slapped together with a goodhearted kind of sloppy naiveté.

The production features a constellation of superb actors whaling away at stuntmen with automatic weapons, generating the sort of apocalyptic slapstick Moe, Larry and Curly would create if they had access to bazookas. Yet the movie manages to keep theatergoers, if not in stitches, at least not in need of safety pins to keep their eyes open.

“Red 2” wheels out aging-but-still-agile Bruce Willis for a second spin as Frank Moses, a retired CIA black-ops man determined to build a safe, risk-free life with his winsome girlfriend. Sarah (Mary-Louise Parker) is bored silly sleepwalking the aisles at Costco; she wants Frank to play the rugged hero.

Be careful what you wish for. The couple soon find themselves targets of a high-tech manhunt by INTERPOL and the Russian and American governments, with a freelance assassin (Korean star Byung Hun Lee) chasing them to boot. Now it’s up to them to save the world, or get really bruised trying.

The plot is a rickety scaffold for a series of car chases, sniper fire and boot-to-head combat, along with the obligatory smooch scene. This is a film where all you need to break into the Kremlin is a sledgehammer and a Russian Army Halloween costume. The intrigue is not exactly credible, but it keeps our interest in who did what to whom and whether they’ll get away with it. Even if you don’t believe Secret Agent Bruce could kill anything stronger than a six-pack of Bud Light, you still want go along for the ride and see what happens next.

Helen Mirren, knee-meltingly gorgeous at 67, returns as MI6 retiree Victoria, with lethal skills as sharp as her loyalties are ambiguous. John Malkovich again plays Frank’s trigger-happy spy partner, Marvin, whose antics Willis regards with the confounded expression of a man peering under the hood of his car. Catherine Zeta-Jones plays Katja, a Russian agent who was once Frank’s lover. And Anthony Hopkins plays addled British scientist Edward Bailey, who is the key to locating a U.S. doomsday weapon hidden somewhere in Moscow. With his tweeds, striped school scarf and absent-minded eccentricity, Hopkins seems like one of Harry Potter’s dotty schoolmasters who wandered off the Hogwarts campus.

The ace cast isn’t an extravagance but a necessity. They con us into ignoring preposterous contrivances and make dimwitted dialogue sparkle like Champagne. When Willis barks at Malkovich for giving the untrained Parker a gun, he chidingly retorts, “This is AMERICA, Frank.” The substance of “Red 2” is not superior. Its sales technique is breathtaking.