You should respect your elders wishes.
Dan's dad asked Dan to pull the plug if he ever forget who Dan is, and it actually happened.
Dan wants to make a decision on his dad's life.
Dan tells the doctors to pull the plug on his dad.
Dan doesn't tell the doctors what his dad wanted wants his dad to stay alive.
Dan's dad doesn't have to suffer anymore, and this makes Dan relieved.
Dan's dad continues to suffer, and Dan doesn't like seeing his dad like this.