There are more people in the world than there is work for them to perform. Progressives see humans as Labor Units to be deployed in various industries to maintain an efficient collectivist economy. If you have more people than work, you need to cull the herd because the non-productive consumer of resources is the worst thing in the world to the Progressive. Birth control is the most humane means of accomplishing this culling. Take away birth control and they give you starvation, wars, purges, along with forced abortions and euthanizations.
Remember that there is no God to these people. Humans = Dogs = Pigs. And don’t fool yourself and think that I’m only talking about traditional liberals here. There are many ultra-wealthy industrialists who believe in this future for the masses too. They hide it in the Green Agenda and the Gay Agenda.
At our current stage of conversion to a communist economy, the Progressives need lots of useless eaters to break the system (i.e. Cloward-Piven). But, the endgame on C-P is almost here and once the system is crushed and the New Communism (in whatever form it takes) rises from the ashes, the Progressives will be very insistent that birth control become the favored means of population control and reduction.
Not only birth control to reduce the population significantly, but Death Panels, too, to rid the world of us older useless eaters.