It means we are equal in the eyes of God not in the eyes of man.
Humans will always have a tendency to measure the worth of a person by their abilities. The state especially thinks like this. People of ability are good plow horses for the state to squeeze. People of no ability make a net negative contribution to the state.
Fascism and other types of socialism are very vulnerable to this way of thinking because they think the function of the individual is to serve the collective. Those who can't serve are a waste of space. This was the attitude behind nazi eugenics operations. They wanted to exterminate or sterilise everyone the state thought had no value. To such people we're just human resources.
Moral thinkers, like God, see the individual as having intrinsic worth, that is not dependent on their capabilities.
This post was edited by Zeitgeist at April 17, 2018 10:32 AM MDT