Why does Draco Malfoy hate Hermione Granger?

The reason why Snape hate Harry Potter is probably because when Snape went to school with Harry's dad he was a jerk to him. Watch Harry Potter and the Order of the Phoenix. When Harry goes into Snape's office Harry goes into Snape's memories and sees his dad hurting Snape.

Another reason is because of Sirius Black (personally my favorite character). According to Snape's memories, Snape was rather shy and kept to himself, which made him a target to Sirius Black and James Potter,whom Professor McGonagall states were always playing practical jokes on people. Sirius knew Snape wanted them caught in the act of becoming animagi (people that can turn into animals willingly, which very few people were and these particular animagi were unknown to most), and also knew that if he followed Black, Lupin, Potter, and Pettigrew he would get beat up by the Whomping Willow (a very violent tree), which guarded the group from being seen. Black let themselves be seen when Snape was there, and let him watch as they went to the spot, all the while Snape assumed he was being sneaky. There was a certain knothole that needed to be pressed (on the opposite side of the tree) which could only be accessed by Pettigrew, who could turn into a rat. Snape ,however, missed this and was walking the Willow when James Potter (Harry's Father) saved his life as he narrowly missed walking a tad further and being killed by the Whomping Willow.

For this reason, Snape was displeased as he hated James, and felt very in dept. Snape insults Harry endlessly, stating that his father was a fool, when indeed he hated James for saving his life.

Another reason is that Snape described Harry as "arrogant" and "a fool, just like his father" as mentioned above. This brings us to the numerous tricks James Potter played on Snape, which, as you know, Snape greatly resents.

Also because when Snape was young he fell in love with Lily. James stole her away.