Libertarians easily concede that people are not
born free and equal. To quote Hayek:
F. A. Hayek wrote:"The liberal, of course, does not deny that there are some superior people — he is not an egalitarian — but he denies that anyone has authority to decide who these superior people are."
However libertarians insist that people are
created equal. Created, in the sense that the legal structure does not recognize any privilege of any group.
Everyone is equal in the eyes of the law, the law will not pre-favour any particular persons or group. An egregious example of where this code was broken was the pardoning of Richard Nixon by virtue that he was a previous president.
I highly recommend reading chapter 5 "Created Equal" in Milton Friedman's book "Free to Choose" for more information on this subtle distinction between
born equal and
created equal.