Logic and Gaia

I am well aware that finding logical inconsistencies in environmentalist positions is like shooting fish in a barrel, but this thought just occurred to me:

We know that there have been vast changes in climate in the past, most notably ice ages and periods of warmer climate in between. One would presume that in the absence of mankind, these shifts in climate would continue. Now, if one can encapsulate a general philosophy of environmentalists, it is that they think Man should have as little impact on nature as possible.

The current issue of man-made global warming (AGW) would seem to fit into their philosophy well: We are causing the planet to warm due to our use of fossil fuels and therefore should take efforts to counteract the changes we are causing. Here is the rub: The data are unclear about warming*, but let's offer a hypothetical--What if there was unequivocal data indicating that the Earth was cooling? By this I mean such clear-cut evidence that there was no doubt in the mind of anyone that the planet was cooling-off by a lot. Whatever the actual cause, does anyone doubt that conservationists would be utterly convinced that Mankind is to blame and that therefore we should take (economy-crushing) steps?

In other words; any detectable change will be opposed by the pro-nature crowd and yet this would seem to violate their basic philosophy. They would have the Earth locked in amber, as if this period in time just happens to be the perfect and ideal climate--when what is natural is for the climate to constantly shift over time.

*Warming or cooling seems to depend a lot on what the baseline is. If you start at the end of the little ice age 1850, then we have been warming. If you start in the warm year of 1998, then we have been cooling etc.