In Into the Wild, why did Chris McCandless hate his parents?
Chris had issues with his parents, in particular, his father. He was shocked when he discovered that his father had another family he had never been told about, and that, in fact, his father had not been married to his mother when he was born. This information made him feel that his whole childhood had been based on a lie.
But beyond that, Chris had deep issues with his parents' materialism. They had worked hard to build a business, but Chris felt that his father tried to use money to control him. Being strong-willed like his father, he chafed under that control, and he decided that as soon as he had graduated from college, he would break free from those bonds.
In college, Chris's reading of countercultural authors such as Thoreau and Tolstoy reinforced his ideas about rejecting materialism. Like many young people, he was trying to establish his own identity, and this, along with his other issues with his parents, led him to reject both them and their values.