Capitalism is a man-made arrangement with a set of rules.
It is, only the rules are (simplistically) "here goes, lets leave eachother alone now.". There is no invetability about the outcomes, but if you mean that people able to create more wealth (whilst observing the rule) become wealthier then whats the problem? If you mean inheritors get an 'unfair' advatnage then maybe thats worth discussing as a seperate issue.
The problem for the poorer folk wanting to take from the richer ones without going through the process of wealth creation is something for people to mediate either rigidly (via rights) or dynamically (via welath destroying revolutions, or hefty policing or paying 'protection' money to the poorer folk to stay away)
The philosophic underpinnings of neo-liberalism or anarcho-capitalism, rest upon the usual "human nature" arguments.
These are not, however, based upon biology but on individual rights of (in America) "life &, liberty" which means that each person owns their own life and not other peoples, and that property rights represent the essential part of liberty, to make that word meaningfull. The history is tracebale to Renaissance thinking and individuals such as JS Mill, Locke, Jefferson etc - its roots are in reason, science (reality) but also in religion. Whatever the reason, rights should be evaluated on their merits in a context of what is real about the nature of mankind as an entity. This is where much of the argument stems from. The accurate description of man as social does not lead to the conclusion man therefore owns man. The basis is voluntary. Care for others is based upon the interests of individuals who form the group, and need not be imposed externally lest we describe ourselves as herd, pride or tribal animals.
"Might makes right" is the ideology of unlimited democracies and autocracies, and specifically conflicts with individual rights.
Ending with the observation that "is to ought" is a problematic process is increasingly better levelled at social structures whose interference (ie, not leaving things as they are) is greater. Ie unruled anarchism to state governed capitalism to socialism to totalitarianism. Each 'stage' represents more social engineering - more messing about based upon an (innacurate) intepretation of "is". To best find out what "is", leave everything alone.