Do these people think the world would be better off if the climate was exactly the same as it was a million years ago? Five million years?
What if no species had ever gone extinct?
Of course things have to change. Medicine has changed noticeably since I graduated medical school and that wasn't that long ago. We cure diseases now that would have killed patients even 20 years ago. The average lifespan is much longer now that 100 years ago.
I don't think I would enjoy the beach during the ice age as much as I do now that there has been some global warming.
Who knows what kind of awesome life forms might develop if we killed off a few species that would have eaten them and warm the place a few degrees?