Hume was simply wrong. You can rely on a chosen authority or you can arrive at your own belifs based on the evidence available now. Again, Hume was very simply wrong.
With much admiration,
In order to show that Hume was wrong you need to show how an ought can be derived from an is. If you can bridge the chasm between facts and values without smuggling in a moral premise somewhere you will be the first to do so, as far as I can tell.
Biological chance cannot serve as the foundation of right and wrong; it is instead their undoing. If human nature and the human mind are the unintentional outcome of the chance concatenations of atoms and natural selection, then right and wrong are accidents, not moral absolutes. There is no reason to trust accidental physical forces as indicators of moral 'goodness'. The very notion is incoherent.
Cordially,