The spectacularly dumb, and weirdly entertaining bad-taste thriller “Bad Samaritan” is the kind of movie that many will assume can only be enjoyed ironically, or just with some sort of emotional detachment. This serial-killer horror flick does, admittedly, sound like low-brow kitsch: former “Doctor Who” star David Tennant, playing vicious trust fund murderer Cale Erendreich, chases after glassy-eyed, under-achieving artiste Sean Falco (Robert Sheehan) in an expressive, sleazy, sub-Hitchcockian battle of snobs versus slobs. Cale is rich and perverse enough to try to ruin the lofe of Sean, a petty thief who makes the mistake of breaking into Cale’s ultra-luxe Portland, Oregon house, where Sean discovers appropriately petrified Helen (Lisa Brenner) tied to a chair just two floors above Cale’s garage-set torture room, where he keeps his Maserati and impeccably mounted tool kit. That being said: while “Bad Samaritan” isn’t exactly a good film, it is weirdly charming, thanks to its creators’ exuberant commitment to unabashedly tacky ideas. “Bad Samaritan” starts out like a lurid stoner horror film. Sean does, after all, conspicuously smoke a joint with his best buddy/fellow thief Derek (Carlito Olivero), a restaurant valet who—with Sean’s help—sneaks into clients’ homes, and selectively divests them of their valuables. This table-setting scene of harmless recreational drug use doesn’t tell you a lot about Sean, but it does cast the film’s slow-burning first act in an inadvertently funny light. Maybe Sean’s status as a stereotypical pothead makes it easier to understand why a later scene, set in an outdoor car-park, is shot with special attention on Sheehan and Olivero’s highly visible breath as it rises from their mouths like dragon’s breath. And maybe Sean’s one-time toke also accidentally explains why there are so many low-key red herring jump scares throughout the film’s first 45 minutes. And hey, how about the film’s dimmer-switch-low lighting, and hazy grey color palette? Maybe this is what it’s like to be the Cary Grant character in a Hitchcock thriller, only you’re super-high, young, and capable of any number of dumb life choices, like trying to call the cops on a super-rich guy with the above-mentioned garage torture chamber. Then again, one of the main pleasures of watching “Bad Samaritan” is puzzling over the barely sensible motives of dim-bulb characters like Sean. This is, weirdly enough, the main appeal of Tennant’s character, an absurdly calculating antagonist whose motives are a great source of mystery (but not really). Cale’s weird need to destroy Sean is that much more tantalizing thanks to his bizarre Freudian backstory about horses, and childhood trauma (it’s hinted at in the film’s opening scene). Receptive viewers are bound to enjoy watching Tennant’s motive-less killer half-scowl and half-pout like Sam the Eagle as he painstakingly dismantles Sean’s life in the silliest, and most aggressive ways. Nothing is sacred, not Sean’s parents’ jobs, not his Facebook password, and not his girlfriend’s college lecture on … glaciers? This movie proves the Oscar Wilde joke about how playing the piano “accurately” is over-rated as long as you play “with expression”: you don’t need to be technically accomplished to make a fun, unsound piece of pulp fiction. There’s even a certain charm to the film’s sleazier scenes, the ones set in Cale’s remote cabin, where he locks Helen up in a a homey jail-cell-like enclosure—complete with designer blankets and Land’s-End-catalogue-quality clothes—that seems to have been home-decorated by Crate and Barrel. There’s not a distracting amount of gore, or nudity in these scenes, though there is some of both. And Cale’s rote serial killer backstory is made much more bearable by Tennant’s gamely hammy performance (the man tears up scenery like Pacman gobbles up pellets). But really, I think what I like most about “Bad Samaritan” is that it seems to have been made by people who bravely refused to be stymied by their long-term lack of direct contact with actual human beings, as evidenced by the film’s tin-eared dialogue. These filmmakers keep on stacking bad ideas on top of each other, like a rickety house of cards, until bombs, literal skeletons, and even baseball-bat-wielding British men—with a weirdly adenoidal North Dakota accent?—are leaping out of closets, premature graves, and convection ovens. So, if you’re now curious about seeing “Bad Samaritan,” a film that is not for everyone: don’t see this movie alone at home. Instead, I urge you to either rent it with some friends, or find a theater that’s showing it—preferably one with assigned seating—where you can sit close to a bunch of total strangers. If you can get on the same wavelength with your fellow theatergoers, you’ll enjoy laughing at “Bad Samaritan” with them. You’ll also probably want to join your new friends in applauding the film’s (sometimes intentionally!) hilarious dialogue. And if you feel a little ironic detachment coming on, just remember: if “Bad Samaritan” works for you, your pleasure can’t be all that guilty.