Because everything looks like one.
Examples
[ARMED LIBERAL] The terrible beauty of essentially unprovable religious beliefs (like the existential risk of climate change) is that they justify any actions you want to take.
[HONOURABLE JOHN] One Religion Is Enough.
[JUDY] If the IPCC is dogma, then count me in as a heretic.
[MATTHEWJ] All have sinned & fallen short. And nature is angry. The only way out is to expiate our sins by doing whatever they tell us.
[REINER] It is perhaps the ultimate irony that the science war about climate change has all the overtones of a religious war.
Objections and Replies
(Belief) Talk of belief shows it’s a religious test around the Climate Cult—
Reply. Alternatively, belief expresses an attitude we have regarding stuff.
(Civilization) I must make a last stand to save Western Civilization—
Reply. Try not to create a Crusade 5.0 while you do, shiny Armored One.
(Cult) Climate scientists form a cult—
Reply. Pray tell more about the true science you presume.
(Dogma) The science has been overtaken by dogma—
Reply. Citation needed.
(Likeness) AGW is like a religion—
Reply. From the hammer perspective, everything looks like a nail. From MC Hammer’s perspective, nothing can be touched. From all the hammers perspectives I know, everything is a nail one can’t touch.
(Prophet) What about this prophet of doom—
Reply. You’re begging #ButCAGW.
(Unproven) The terrible beauty of essentially unprovable religious beliefs—
Reply. You mean, like the speed of light?
Notes
{Censorship} One variant of #ButReligion hints at censorship or mobbing: Salem, heresy, Luther, etc. The most famous form is of course #ButGalileo.
{Everything} There’s little easier than to compare something one does not like to a religion, at least when one hasn’t done any kind of religious studies. Everything is like a religion except religion, which is like a language game.
{Manicheanism} The square can be used to whine about confrontation: creed, heresy, persecution, stigma, etc.
{Millenarism} The square can appeal to #ButPredictions, e.g. prophecy, doom, etc.
{Spychology} The square can offers a mind probe: bigotry, cult, dogma, fundamentalism, mass hysteria, zealotry, etc.
{Toleration} The religious vocabulary has seeped in common usage: pontification, ex cathedra, etc.