That statement is incorrect. Liberalism is based on believing in a moral equality of human beings (a belief I share) and believing in the existence of a priori 'Rights', such as "Natural Rights" (a belief I do not share). Those are beliefs, not "empirical observation."

I am convinced that I have discovered an ethic of justice that does follow from the observation within material existence that human beings have no choice but to effect choices. That makes the capacity to choose integral to being human.

That observation can be verified by all people. How and why a requirement for all human beings to respect the capacity of all other human beings to choose for themselves follows from that observation is obvious. The implications for individuals, the political process, and the economy follow from that ethic of mutual respect (in effecting choices) as certainly as day follows night.

This ethic of justice takes our understanding of justice beyond Liberalism.