They actually have principles - only they are exceedingly bad ones.

They believe in the fundamental value of the environment. But the environment means 'that which surrounds you'. Though they sometimes claim to be preserving 'that which surrounds you' for the sake of 'you', they usually act to preserve 'that which surrounds you' whenever 'you' try and change it. 'Greenpeace' and 'Earth First' do literally mean to put the Earth before any human interests. In trying to preserve 'nature' they deny man's need to exist by using nature.

Thus environmentalists are the ultimate statists - they want to control every industry, product and person to make it 'help' the planet. To implement any of the major environmentalist policies, such as energy taxes, banning CFCs, and 'sustainable development' is to take a step back towards the Dark Ages.