People should not sever relationships with family without good reason.
Biff lives with his parents who are strictly religious.
Biff wants freedom to explore other worldviews and lifestyles.
Biff calmly explains his feelings to his parents and continues his personal exploration.
In frustration, Biff moves out on his own and cuts ties with his parents.
Biff is free to explore and though his parents disapprove he is still a loving family member.
Biff is free to explore but misses out on the emotional support of a family.