Referring only to the three tendencies (to have our emotional state influenced by the emotional state of those around us; our feelings about our own situation are influenced by how we see our own situation in comparison to that of others; that we like pleasure and try to avoid discomfort or pain), Hume explains our moral views and even our belief that our moral views reflect not our human biases, but, instead, something objective.

To make for an easier time maintaining consistency, allow me to speak as though I were in fact Hume, making all statements using the pronouns “I” and “me.” Further, please keep in mind that I am basing this post strictly on assumptions, and am not claiming to be certain or to be any more correct that any other proposition.
I should like to think that because people tend to be such social beings even the most complex concepts, the very foundations of our existence (in this situation moral views), are influenced significantly by others. Because we are so aware of the emotions of those around us, because we experience such empathy for the important actors in our lives, and because we are so controlled by emotion, it is relatively easy for the feelings of others to sway our beliefs and resulting actions. Morality is determined by society. It is dictated by those who are persuasive and powerful.
As for the question of whether our moral views reflect our human biases or something objective, I disagree with the concept of human biases in this context in general. If we agree to continue with the line of thinking that says that people can be swayed by others’ feelings, then I think it is safe to say that “human biases” is an inappropriate term here. Allow me to explain: if it is a human bias for one or a few, can it still be considered a human bias when it applies to everyone? Maybe you disagree with me, but I think that once a “human bias” has been embraced by so many (in this case the majority of the world’s population), it stops being a human bias and becomes a social norm. This then is in direct support of the idea that our moral views reflect not our human biases, but something objective.