The earth carbon-cycle affecting the temperature of the planet as a whole is a theory just as valid or invalid as any other theory... nothing more nothing less.
Nope, if you criticise this theory as a scientist you get all your funding stopped and you get excommunicated. If it can withstand critique why does the theory need protection?
Theory only needs protection from leaders if said theory gives said leaders more power... Humans only protect what they are genetically dispositioned to protect including power.