Unless you spend your entire life in some kind of isolated monastery, it is inevitable that you will encounter some very different views about God to your own. Any Christian can tell you that God is our Heavenly Father, but in Islam, such a concept does not exist. What do we say to this?
Muhammad's back story is quite the tragic one. He never had a consistent father figure, and as a result, he never really understood what it meant that God is our Father. To Muhammad, the discipline of God means He can't really be our Father.
But as God asks us in Hebrews, what son is there that a father does not discipline? Put simply, Muhammad got it backwards. The discipline of the Lord is not proof that He isn't our Father, but that He is. A good father disciplines his children. When a child does wrong, the father corrects that wrong. When a child is weak, the father pushes them to do better.
Discipline corrects faults. Fathers correct sons. When God disciplines His children, He is not disowning them, but pulling them towards Himself. If we are to bear the image of God, it is to be expected that we will be disciplined for failing to do so. We can all be grateful that God isn't as distant and angry as the Qur'an claims He is.