"Are greenhousers simply believing that climate should be constant and any change can only mean humanity is sinfully responsible?"
No. Climate scientists have evidence that digging up carbon desposited when dinosaurs roamed the earth and bunring it has increased the probabilty (as we've cleared much of the world's forests) of a return to a violent dinosaur-era climate - but mercifully minus huge carniverous dinosaurs!
The worst part of what is going to happen (unless we work like crazy to reduce our output of CO2) is not meaner droughts and meaner cyclones, it's an ever accelerating rate of ice-cap and glacial meltdowns as the area of heat-reflecting white diminishes and the area of heat-absobring dark colours creates an even faster rise in global temps than even the most gung-ho scientists had predicted!
If you're standing in a paddock being charged by a carzy bull, that is not the time to use your pocket calcuator to evaluate the best fence to run towards (the closer uphill fence of the further-away downhill fence) and phone a fence advisor on your mobile for a chat about fence options.
If you're standing in a paddock being charged by a crazy bull, pick any fence and RUN LIKE HELL and hope you can jump over it before the bull gores you in the backside.
This not the time for twee middle-class discussions about does climate change really exist - or is it a plot by pinko-scum radicals who hate capitalism?
Just about all climate scientists have evidence that backs up the therory that it does exist and it was mostly caused by humans and that if we dramtically reduce our rate of CO2 emissions we may eventually be able to stop the crazy bull before he gores our only habitat into a state not fit for human life as we know it.