No, not the We-Should-Prevent-Damage-To-The-Environment-By-Use-Of-Clean-Technologies kind of environmentalists, but the People-Are-Too-Stupid-To-Understand-That-We-Know-Better-Than-They-Do environmentalists. They are sometimes referred to derisively and deservedly as as Watermelon Environmentalists: green on the outside, red on the inside. They use environmentalism as an excuse to promulgate their socialist agendas since a straightforward approach would be rejected out of hand, particularly by those who suffered under the more extreme forms of socialism in the past.
A good example are the more rabid Anthropogenic Global Warming crowd, the Goristas, those wishing to drive us back 100 years or more to a version of Utopia that never existed. They figure that technology is the problem and that more technology, even green technology, isn't the answer.
Remember the great controversy over cold fusion? Two scientists, Martin Fleischmann and Stanley Pons, claimed that they had achieved fusion without high temperatures and elaborate magnetic bottles. If they were right — and very few scientists now think they were — we might have had a wonderful new source of cheap energy, with little pollution.
Not everyone thought that was a great prospect. In fact, a few extreme environmentalists openly said that they hoped that Fleischmann and Pons were wrong, that we did not have a wonderful new source of cheap, low pollution energy. (Even though it might displace other sources of energy that caused far more pollution.) For these extremists, providing more energy for people was wrong, in itself.
So when I saw these extremists oppose a potential source of cheap, clean power, I wondered what they had against civilization, and further advances in civilization. Reporters at the time did not share my curiosity, and so I never saw an answer to that question.
If a virtually inexhaustible, cheap, clean source of energy became available, civilization would be transformed. Our high-tech civilization might become a hyper-tech civilization, one that only large amounts of energy could supply. It might also mean we could finally spread out through our solar system, and beyond. This terrifies the watermelon enviros because it means they would be less and less likely to be able to control the people they see as the great unwashed masses, those not enlightened enough to understand that only they have The Answer to all of mankind's problems. They would prefer us to return to an agrarian society as it existed at the beginning of the 20th Century, or even earlier. Of course they forget to mention that our lifespans would also be reduced to that of our ancestors because much of the medical technology would also be banned at some point. The only ones receiving the benefits of 21st Century technology and energy would be the overseers, those same watermelon enviros. After all, they have to keep an eye on the rest of us, the unenlightened.
Some may remember a forced return to an agrarian society has been tried before. The Khmer Rouge tried it in Cambodia, killing about a third of their population in the effort. It didn't work. There's no reason to think the Goristas would fare any better.