thats an interesting thought, that he should have turned out cold i guess. However i think that he hated the Dursleys so much he in a way subconsciously forced himself to be the opposite of them. And it just happened that the opposite was nice, caring and able to love. Also i think we hav to realize that this is a fictional story and it wouldn't have been very good if our hero was as mean and evil as Draco Malfoy.