Kind of like how, in a broad sense, it would be good for the planet and good for society if we killed half the people on Earth right now, today. Of course, we could really never, ever do this, as we care about those people's lives.
I hope that doesn't sound psychotic... my point is that it is evil, the enclave is evil, but only in the sense that they look completely past emotion and empathy toward a very scientific goal, with possible, however hidden and misguided, good intentions.
It does sound a tad unplanned, however, as a person with the amount of logic capable of making a plan to better the Earth would take into account that much of civilization as we know it would collapse, as removing half of the entire human population would screw over our workforces world wide, and paranoia would run rampant towards when the next purging would occur, and the remaining humans would care about their own lives a lot less, seeing as how so many could be wiped out without a second's hesitation.
Seeing as how many potentially destructive things are manned by more than half the human population, the now un-controlled ships, vehicles, planes and so forth would crash, killing even more animals, oil tankers simply crashing and spreading oil across the oceans etc.
So, in fact, it would ruin society, and immensely harm the environment if we were to just kill off half of our own global population.