I think there are two kinds of environmentalist - the purist kind you prefer and the practical kind. The practical kind has the arguments that appeal to most people with things like "let's not run out of oil because it's useful" and "lets not cause climate change because it'll lead to problems for people". But the purist kind is really more of a religious belief that you can't persuade people of in practical terms. That doesn't mean it's wrong - it's just that even adherents don't know why it's right, if it is. Just like religion. You see the purist kind extending to things like "lets not colonize the moon or Mars because we'll damage their natural state." Maybe in a million years, they'll turn out to have been right, but nobody knows that today.