Billy's father says they can't stay with grandpa and grandma cook because he and Billy's mother are getting a divorce.
Because of the fact that Billy's parents are separating, he can no longer stay with his grandparents, but rather go to a court where the judge will decide where the child will live from now on - whether that is going to be with his mom or his dad.
Answer:
Dr. King's message in my opinion, was basically just telling us to have hope; "wallowing in despair" means to lay or bask in loss or absence of hope, but Dr. King tells us not to do that.
