Cult.
When and if they ever get up and running and have any real power over a group of people, they will find that human nature is unchangeable and that their Utopian precepts are unworkable.
That will, of course, lead to another Jim Jones Kool Aid party and mass murder.
Just the fact that someone thinks that the ideal human population worldwide is only 500 million - that will require mass murder to accomplish. Assuming a current population of 7 billion, that means that 6.5 billion people have to go. That's over 90% of the population.