Conservatives have cobbled together a strange world view. They do not, largely, believe in biological evolution but they do believe in 'social Darwinism' (which Darwin himself did not). At a very basic level, the problem with 'survival of the fittest', as an ideology, is that it directly contradicts the basic principles that modern, western democracy was founded on.
Underlying the basic constitutions, laws and other documents which laid the foundations for modern representative democracy was the 'social contract'. The social contract, for those who don't know, is according to Merriam Webster:
"An actual or hypothetical agreement among the members of an organized society or between a community and its ruler that defines and limits the rights and duties of each."
More specifically it is the theoretical foundation of civilization itself. According to philosopher Jean-Jacques Rousseau, whose ideas were instrumental in the French and American revolutions again from Merriam Webster:
"Rousseau held that in the state of nature people are unwarlike but also undeveloped in reasoning and morality; in surrendering their individual freedom, they acquire political liberty and civil rights within a system of laws based on the "general will" of the governed."
But, the idea of Social Darwinism sits in opposition to this idea. While the social contract may, in theory, keep you from attacking your neighbors and stealing their food it only works so long as you have the ability to acquire your own food.
This may not have occurred to the framers of the American Constitution or others of their era. At that time an individual could, if cities failed to provide economic opportunity, strike out on their own. In the United States of the early 19th century (as well as Canada and most of Europe) an individual could pack up their family and belongings and head into the wilderness. They could build a small dwelling, farm, hunt, fish and 'live off the land'. In 2013 that is no longer possible. In a world with a population of 7 billion people, virtually any and all land capable of supporting human life is claimed either by private citizens, governments or both. This is where the 'contract' idea begins to break down.
In the early days of man, social Darwinism was largely how things worked. If your neighbour had food and you needed food, you could hit him with a rock and take it. In theory we abandoned this approach and formed "civilizations" to get away from that approach. We entered into a social contract which took away some of our freedom, but prevented us from being hit with rocks. At that time it seemed like a good idea. There was, no doubt, poverty but there were cures for it.
In 2013 the game is rigged. Tax policies have concentrated a great deal of wealth at the top and, contrary to the promises of Reagan and Thatcher, none of it 'trickles down'. Life continues to get more expensive, but incomes for most people haven't gone up in decades. Meanwhile 'austerity measures' largely based on bad math have gutted programs meant to help people in the bottom 90% of income brackets. If you're willing to take on massive debt loads you can go to university but, currently, that gets you no closer to a good job or a better income. (As a side note, any good historian will tell you that a mass of unemployed or underemployed university graduates is not a sign of good things to come.)
So, let's look at that contract again. After all a contract, in order to be valid, must be entered into willingly with both parties getting some benefit from it. So, someone puts this contract in front of you today: The contract says that you will not steal, or kill, or assault, or use drugs or jaywalk. It also says that you can 'look for employment'. In the fine print though it says that the job situation doesn't look good, and may get much worse. Also the social safety net and programs designed to help you to succeed have largely been scrapped. In other words a system of "survival of the fittest" where "the fittest" had already been chosen, but where you were free to fight over the scraps so long as you didn't bother anyone important. Also, the "rights" that were originally guaranteed to everyone had been scaled back in order to keep people from bothering anyone important. Would you sign that contract as is?
If the answer to that question is "no" then the contract isn't valid or binding and we have a huge problem. If the social contract isn't valid or binding then people may be legally or morally prevented from acquiring goods "by any means necessary" but they are not really ethically prevented from doing so. U.S. prisons are filled with people most of whom found it impossible to survive within the system and all of those people will find it harder, not easier, to make a living legitimately on their release.
The social contract is, quite simply, broken. It is null and void and needs to be repaired. Conservative social Darwinist approaches offer no solutions. That approach has utterly failed and has only been practiced (in the pure form desired by the far right) by the most brutal, violent and repressive societies in human history. Even in the our days as nomadic hunter gatherers a skilled or lucky hunter would share with their tribe and not horde provisions while their clansmen starved.
If we are to survive and avoid violent upheaval we have to renegotiate the social contract for the world we live in, rather than the world our ancestors did and create a situation, globally, where the basic necessities of survival and the basic tools for self advancement are guaranteed and unalienable. The only alternative is a slow decent into brutality and chaos that could set civilization back centuries.