Reality is not so dichotomized. Human choices are influenced by both nature and nurture (i.e. environment). In psychobiology, I believe the consensus is that nurture contributes at least 50% to personality development and consequently propensity for certain choices and behavior. If inherent nature can't be changed, how could have the environment been different, to change the outcome? That was what I got from the parent comment.

By the way, if we're talking about "fundamental" qualities of a person -- from a biological standpoint, there is some evidence for a genetic propensity toward 'good' (e.g. altruism) or 'bad' (e.g. violent) behavior. But the vast majority of people land somewhere in the middle.