Im Catholic but I support Social Darwinism
No,i do not believe that we should murder poor people,but I support the idea of Herbert Spencer.
Competition is a natural process of all societies, and free markets or deregulation is the most efficient way for economy to prosper -- anyone who's a true right winger understands that, and it's in part because it's the best way to sort out the most skilled. It's a natural hierarchy. Kind of like bubble-sort in C, but applied to people, it filters people from best to worst. You just apply that sort of thinking to wider society, with practices that ensure only people who are "fit", both morally and biologically can reproduce. Spencer is the one who coined the term "survival of the fittest", and his writings led to the rise of so called "Social Darwinism", as a philosophy, but it was not really applied in the way Spencer envisioned or wrote about. It's mainly the idea that societies can evolve, metaphorically, as organisms do. Learning and adapting to situations to suit their interests in an organic society, which can be understood as when the recognized power and the actual power are the same. Otherwise, you will confuse yourself applying this theory, because societies that don't align the two (democracies) do incredibly dumb stuff and learn nothing, consistently. Most rightist libertarians are social darwinists in some sense, really.
"How is this compatible with Catholic Social Teaching?"
It's charity. I believe it's a highly immoral to ignore anyone who is struggling. Charity exists to make up for life's unpredictability. I'm anti-welfare, I don't believe in coddling or extreme dependency on a social level. Charity gives people a chance to live well, even if they don't evolve, and that's fine. Competition is a means to make life better. It's a means to "evolve" on a wider scale. Voluntarily providing for someone who legitimately cannot work for health reasons, is fine. It doesn't hinder anyone else unjustly, it's not parasitic. Jesus said that it's "the sick who need a doctor" when he dined with sinners to try and redeem them. He didn't approve of what they did, he called it a sickness, he wanted to help. Charity is the same thing. If they are truly unable to help themselves then the charity will result in them back where they started from their own actions, and they'll be judged for how they lived. Ignoring anyone poor would be like a company denying you a promotion forever because you got struck by lightning and had to take time off work to recover.