The Outlander, I once did a study on what God calls for government (kings and princes) to do and was surprised to find out that He gives government little authority to do anything ... certainly no authority to help those in need or do charitable work. Kings and princes are called to be righteous themselves, ensure justice is done, to be sober themselves but that is about it.
Libertarian is darwinian in terms of thinking? I think just the opposite is true. In libertarian thought it is immoral to initiate the use of force or fraud and Darwinism teaches survival of the fittest which is kind of hard to do when you can't initiate the use of force.
The problem with socialism is you always run out of other peoples money.
The first point is valid in some respects, I mean, the bible does clearly set down laws for society etc, and whether nor not you or I support those is another argument. To ensure justice is done, surely one should help the poor, I see no distinction between helping the poor and being righteous. If as you say, God gives the government no authority, does that mean we should all ignore the government? Government can be good as well as bad, governments can topple dictators (or establish them), so to say that the government has no authority is to ignore reality. Yes, God may have a grand plan, but he also taught people to respect positions of authority on earth (to an extreme point in my opinion).
Just because it isn't mentioned in the bible, does that mean we should do nothing about it, the bible doesn't have instructions on new medicines (because it isn't a medical health book, admittedly), does that mean we should ignore new medical discoveries? It doesn't mention particle physics, just because something isn't mentioned, doesn't mean we ignore it. God may call for certain things, but does the fact he's silent on the issue (although the bible does have slightly monarchist undertones at sections) mean we should ignore a topic?
As for Libertarianism, yes, like marxism, in an ideal world it would work perfectly (i.e in Marxism everyone would ideally be truly equal and rewarded on the basis of their own achievements in very much the same way).
Libertarianism is based on the idea people should have economic freedom and not be taxed (or minimalistic tax), as a result, a number of entrepreneurs rise up based on their own good ideas. They employ people and everything is fine for a while (excluding the fact that with minimalistic government, they are not accountable for what they do with their money). The government says; 'we won't tax you, but you should give money to charity and help support the needy'. Now, in response, approximately 70% of the people stick their finger up, don't give to charity (as the bible says all humans are fundamentally evil) and continue on with their lives.
Without government support, people are either stuck in one of two categories; the entrepreneurs who make all the money or the larger class of workers, who survive on whatever the entrepreneurs dish out.
An Economic crisis comes, the government has no money to act and so the entrepreneurs bail the country out, buying up what's left of public services, the crisis also means unemployment but as the government has not been taxing people, it's left to the discretion of the economy, which is ruthless.
Capitalist, sadly, does not take into account people's feelings or social issues, it is a raw drive for commerce, capital and expansion. Those at the top exploit those at the bottom (The company I work for, for example, sees approximately 2000 pounds per employee coming in each week, it's doing extraordinarily well, but I'd be lucky to see 200 of that), Libertarianism is how aristocracy arises, people inherit businesses which become so powerful and competitive, they destroy smaller business.
I refuse to see how the survival of the person best suited to dealing with the economic climate is different to the survival of the animal best suited to dealing with the physical climate? Why use force? If people are in an area where one entrepreneur owns all the business and is not accountable to government, what can they do? It's a case of working for them or not working at all.