Chris had fought with his father Walt's authority, mostly through passive-aggressive means, all through high-school. He felt that Walt was trying to restrict his mental growth and tie him to societal norms. Chris judged his father by his growing idealism, and refused to compromise those ideals.
When he graduated high-school, his sister Carine recalls that Walt gave Chris an expensive telescope at his graduation party, and Chris became very emotional:
"He was almost crying, fighting back the tears, telling Dad that even though they'd had their differences over the years, he was grateful for all the things Dad had done for him. Chris said how much he respected Dad for starting from nothing, working his way through college, busting his ass to support eight kids.
(Krakauer, Into the Wild, Amazon.com)
This moment of personal, emotional connection was rare for Chris, who tended to judge people and remain aloof. Although he did not repeat the performance, his friendly letters and postcards to his family (possibly sent as part of his desire to seem normal) show signs of love and interest. It is likely that Chris simply wanted to find himself before he matured enough to understand and accept Walt for the man he was; his reaction at the party showed that whatever else he felt, he was an emotional human being underneath, and that his connection to his parents was stronger than he knew or cared to admit.