Obviously I didn't mean environmentalists want us to have less sex.
But the essence of my claim is twofold:
1. There is a difference, in my mind, between preserving nature so our descendants may enjoy its resources, or for reasons of out own safety - and between preserving nature for nature's sake. One of these things I find an excellent and wise proposition, and the other - deeply creepy. Unfortunately, the conservation/environmentalist movement these days seems to be more and more dominated by the latter.
2. While there are in theory many solutions to global warming, the main way to reduce our carbon emissions - and probably the only viable one if we want to reduce them by a major fraction at the current technology level - is to consume less.
Coincidentally, a lot of people who take a ride on this are people who, for previous ideological or cultural reasons, dislike Western consumerism. Leftists, for example, have attacked Western consumerism since at least Thorstein Weblen.
Therefore an equilibrium has been forged wherein the theory global warming is attacked (or defended) not based on its actual science (which is too arcane for most nonspecialists to comprehend), but based on the debaters' opinion on Western capitalism and the consumerism that drives it.
On both sides, too.