Their insistence on incontestable veracity sounds like religious fundamentalism (always dangerous). Indeed climate change has many religion-like features - apocalypse soon, guilt-tripping, absolution via carbon credit indulgences, a mythical Garden of Eden, plenty of proselytising career opportunities, and money to be made from donations to the cause.
Climate has changed ever since our lively little planet was but a freshly agglomerated ball of stardust. Islands, glaciers, ice ages, species and mountains have come and gone. Seas have spread and retreated, storms, floods, blizzards, droughts and fires have raged. Volcanic eruptions and meteorite strikes have darkened skies. Lovely days have dawned. It's all normal. When the climate stops changing I will worry.
The planet will be fine; humans though - perhaps not.
People have foolishly built cities built on natural flood plains, on reclaimed land and on low-lying coastlines where essential infrastructure is vulnerable to the natural consequences of meteorological forces, which would be no problem to the planet if humans weren't in the way. They have also acquired instant global communications which mean every passing weather event is sensationalised wildly, and hysterically cited as proof positive of climate change.
Recently though, a wise young person pointed out to me that, whatever the truth, if enough people think climate-change is a problem, then it is a problem ... a bit like hypochondria.
Acceptance of this truism reached critical mass recently with nearly 200 countries sending junketing negotiators to climate talks in Paris. The deal boiled down to who pays whom, when and how much; business as usual.
Global warming targets will have zilch effect on planetary weather, but someone will get rich and I daresay 200 countries' delegates, flunkies and security details boosted profits temporarily for airlines and Paris hostelries.
Of course, humans do affect ecosystems. It makes no sense to poison the very earth and water which sustain us, to conduct wars, to deforest or to plunder finite resources to feed global capitalism's appetite for incessant growth but money is the problem, not the solution.