(The following was the response I made at on a public message board to that exact question.)
I have an uncle who's a born again Christian. He's a very blue collar kind of guy who grew up in a family of mill workers. He never went to college, and worked in a mill himself as a young man, as well as being a volunteer fire fighter in his small New England farming town. He's also an avid outdoorsman and a hunter, getting licenses every year for turkey season and deer season. In addition to all of this, he also tends a magnificent garden in the back yard, growing prize pumpkins and squash. The wall of his den is covered with dozens of blue ribbons from many years of entering his pumpkins and squash at the local fair. He has blue bird houses in the garden, and regualrly bird watches with a set of binoculars from the back porch. There's also a brook running through their property that he has landscaped himself with stone liners on the banks. As his wife says of his gardening and his affinity for the outdoors: "He loves to play in the mud."
Their country home has a wood burning stove in the basement, and so he stocks up on cord wood every fall in preparation for the winter. Many times I have seen him chopping wood in the back yard, and even dismembering a fallen tree with his chain saw. He's always said the best cure for any ailment is to "go out in the yard and chuck a cord of wood --that'll heal ya right quick. It does a body good."
Back in his mid-20's, he went to the state police academy to become a state cop. And when he graduated they said: "You can either be a state highway patrolman, or a state game warden [aka an environmental police offcier]." With his great love of the outdoors, he naturally jumped at the chance to be a game warden, and he recently completed 40 years of service and is now retired.
He is VERY aware of the environment, subscribing to magazines about hunting, wildlife, and gardening. He regularly watches the Discovery Channel and Animal Planet. And his many years of training as a game warden meant he had to periodically attend formal classes on wildlife and on how to handle the various species in his jurisdiction (racoons, eagles, deer, etc). The kinds of phone calls that would come in to his office or even sometimes at his private home included please for help whenever a motorist might have hit a deer down the road, or maybe a demolition crew knocked down an old barn and discovered a nest of baby owls, or perhaps a bear wandered onto someone's property, or else a racoon had got loose in someone's house. He also was in regular contact with various science professors from the local universities, and has sometimes been asked by those professors to assist with injured/orphaned animals in the area. More than once he has taken home a displaced owl or an injured racoon, and spent many months nursing such a creature back to health again.
His knowledge of animals and wildlife --even exotic species from around the world-- is amazing. We were all watching "Who Wants to be a Millionaire" one night, and the question was "Which bird has the broadest wing-span: eagle, condor, albatross, or heron?" And he --a man who barely graduated high school and who pretty much never knows any answers to any quiz show questions ever-- shouted out "CONDOR!" (And he was right.)
His monthly (or is it quarterly? I don't remember) subscription to International Game Warden Magazine includes in-depth articles about the activities of game wardens all over the world, such as wardens in Africa who protect the elephants and lions etc, and the wardens in Australia who protect the kangaroos, crocodiles, coalas, etc. (And there's always a special tribute in every issue to those game wardens from around the world who get killed in the line of duty, sometimes due to an attack by a ferocious animal, and sometimes due to the homicidal aggressions of illegal poachers. Poachers in Africa, Canada, and Florida seem to be the most notorious for not only resisting arrest but actually attacking and even killing game wardens.)
My uncle is a Christian, AND a blue collar sort of a "good old boy" (albeit a Northern/Yankee vartiety of good old boyhood) and he is absolutely convinced that global warming is a reality. He didn't ALWAYS believe in it and actively scoffed the idea for years. But for him, the turning point came when he was reading the enviromental studies about how polar bears are losing alarmingly high percentages of body weight each year due to the rapid diminishment of their ice-based environments. And that data was further bolstered by articles in International Game Warden Magazine about the current concerns being voiced by Canadian game wardens over the plight of the moose and caribou who are likewise suffering as their not-so-snowy-anymore environments rapdily change for the worse every year. My uncle is indeed a believer now.
Meanwhile, I had been hearing for years (decades actually!) from various Christians that global warming was a myth. A paranoid delusion. So I have likewise witnessed this blind and defiant denial amongst Christians that the OP speaks of. Why were so many (at least in MY circles) Christians almost universally convinced it was all a lie?
I must concur with the OP: I believe it was a sad case of guilt by association.
The traditional bastion of environmental concern has always been a particularly ill-liked (ill-liked by many conservative American Christians) segment of the political left: the save-the-whale, save-the-snail-darter, crystal-wearing, tree-hugging, vegetarian, new-age crowd (I realize this is a sweeping generalization, but that sort of broad-sweeping dismissiveness is part of the problem here). So if THEY are the ones who are the primary proponents of this global warming stuff .... then seeing as how they're most assuredly wrong about their crystals, and wrong about their priority of valuing a snail darter over an unborn fetus, and wrong about that whole "harmonic convergeance" thing (anybody here remember "harmonic converegeance"?), and wrong about reincarnation (according to the Christian viewpoint), then surely they are also wrong about this global warming nonsense. The only other discernible voice of agreement about any of this global warming stuff seemed to hail from a particularly laughable sub-category of B-films that began in the 1960's --the "nature fights back" sort full of mutated animals --the kind of film you only ever saw around 3 in the morning on the local independent station. So without a CREDIBLE second party to back up that already ill-regarded first party, most Christians (like my uncle) just dismissed it as a non-issue, no more worthy of their time than claims about UFO's and Big Foot.
My blue collar uncle always had little tolerance for the crystals and the Birkenstocks and the harmonic convergeance. He got annoyed during more than one of his own private hunting vacations and left the forest in angry silence whenever a team of anti-hunting activists would show up wearing their orange vests and loudly scare away the deer. He would read in furious tears about lumberjacks in the Pacific Northwest who would lose their limbs or maybe even their lives because their chain saws had riccocheted off of a porcelein spike driven into a tree by an anti-deforestation activist. He rolled his eyes at the commune down the road where about thirty hippies lived together in a 200-year-old, 10-bedroom farmhouse. And he very diplomatically kept his mouth shut and focused on the conversation at hand while attending a business-as-usual meeting with a local university professor who was obviously wearing a crystal or two herself. None of this was TRULY an "us against them" mentality of straight up hostility by Christians (not typically). It was more a pitying dismissiveness toward them --a sad condescension of their blind misguidedness and their need of Jesus.
So I share the same theory as the OP that because these claims of global warming wafted PRIMARILLY from the same ranks as all of the above sorts of people --people that my uncle found either amusing, pathetic, or criminal-- my uncle naturally marginalized their doomsaying claims, right along with their harmonic convergeance .........
.......... he and about 40 million other American Christians ............
.......... for the past 30 years ..............
........... but then he read the data on the polar bears.