Values
Most people have them: moral propositions which they value.
Values do not stand by themselves or originate in themselves. They are valued because they produce emotional responses, which are biological in nature. Thus it is that values are at least partly a function of biology.
I personally have strong reverential feelings about human liberty. Indeed, it can just about be said that human liberty is my only value, and any other values I have are merely different aspects or subsets of my reverence for liberty.
I can say with some certainty that culture, nurture, and society did not make me this way. These forces mostly value fairness and not getting hurt, both of which are antithetical to liberty. I valued liberty before I could define the word.
The advantages of egalitarianism in a primitive society are pretty clear, and primitive societies tend strongly to be egalitarian. The evolutionary advantages of liberty are more troublesome to understand, but clearly there is some advantage: liberal societies tend to be much richer and more powerful than their socialist or authoritarian counterparts.
Whether you value liberty or fairness/equality isn't really up to you, or anyone else. It's inherited biologically, and nurture can only have limited effect on the moral character you finally assume. And argument will always, always fail to change your values. You may experience strong moral feelings about fairness. You may state your argument in such a way that it strongly engages your feelings. You will then be amazed and possibly offended when I do not respond the same way. It's not that one of us is wrong. We're just working from different base values which are hardcoded in our DNA. You can't persuade me against what I was never persuaded of in the first place.
Often I have appealed to the moral principle of liberty in my arguments with progressives. It would be too much even to say that the argument falls flat. The argument is literally incomprehensible. I might as well argue for toin, or spurl, or plinuckment. To a progressive, "liberty" is a nonsense word, a concept outside of human experience.
People tend to get pretty self-righteous about their values. But if values really are as heritable as the natural sciences are finding them to be, then being self-righteous about your values is morally the same as being self-righteous about your skin color. It is bigotry, pure and simple.
The staunchest lover of liberty can be persuaded somewhat of the necessity of fairness and equality. Those moral values are primal; they came first; indeed they seem to be shared by non-humans. Liberty somehow evolved to be a detectable historical force in the last 800 years or so. Not everyone has inherited it yet. But liberty is a necessary component of modern civilization. Societies that discard liberty invariably become murderous, weak, and destitute. So if we libertoids can't argue our values with progressives, at least we can argue empirically.