Of course desalination is going to require more energy, which is why the 'activists' oppose every energy project that comes along, even these: [link to solar farm v. brown tortoise].
If there's an opportunity to stick it to the human species, they will take it.
First of all, like any group, there are factions within that place different priorities on different things. Take for example, the split in the Republican party between the social conservatives and the libertarians on issues like medical marijuana. Or between the business community and the law & order faction on illegal immigration. What's going on here is a battle between conservationists and green energy people, but you can't just selectively pick one faction's views and attribute it to everyone under the same tent. That's just as unfair as when liberals were screaming "Blood for oil!" about Iraq when there were a wide variety of reasons that Republicans thought the war was a good idea.
So the second thing is that neither group is motivated by wanting to "stick it to the human species." That's ridiculous on its face, and I think you have to know that. The first things you should think when looking at a political cause is, "Why would idealists support it?" and "Why would selfish people support it?" Then, evaluate any claims the opposition makes in that light and see if they pass a sniff test or if they just sound like self-serving demonization.
People who want to preserve other species aren't doing out of hatred for humanity. They have a variety of idealistic reasons: some have a desire to preserve the turtles for the future generations for aesthetic and utilitarian reasons, some think it's a matter of the other species' right to exist alongside us, some worry more about the way that removing a species can have massive network effects on the environment in unexpected ways. Then of course, there's selfish reasons like NIMBYism, e.g. Cape Cod windmills. No one is going, "Ha ha! Another blow against the human race!" (Well, okay no one but a few nuts, but every political group has got a few.)
So, no, that's not the reason. You may have different priorities from conservationists, but you do yourself and the country a major disservice by claiming your foes are all baby-eating monsters. Nothing of value will get done in this country again if we don't all learn to talk like adults to each other.