I can only answer this from my own perspective. To me, cruel treatment is any kind of treatment inflicted selfishly and with the intention of minimizing and hurting the other person.
In Cecelia's case, expecting her children to eat their supper is not cruel. Refusing to let the children eat cookies without finishing their peas would also not be cruel. The purpose here is not to "show those children who's boss." The purpose is to be sure that the children are getting the nutrition they need.
Locking the children in a cage or giving them hour-long beatings because they didn't finish their peas would be cruel. It strips the children of their dignity, and is intended only to "put those children in their place."
I have trouble trusting others or believing that I'm good enough. My relationship with my parents deteriorated after we started going to church. (Among things we were taught: Good children never question authority. Hurt feelings just show that you're not right with God. If your parents are belittling you or otherwise saying hurtful things, it's because you need to learn humility. Only the most rebellious children speak up for themselves instead of just "meekly submitting to God-given authority. "The only response I ever want to hear from you is, 'Yes, Sir.'")
That upbringing severely affected my relationship with both my parents and the "men of God" who preached those philosophies. When I came home from Christian school crying because I was having trouble in science class (and the teacher obviously hated me), my stepfather's only response was a mocking, "Awwww...did somebody hurt your little FEELINGS? That's right! Go to your room and cry about it! Can I come to your pity party?" That was followed by his calling to my brother, "Hey, [X], we're having a party in here! You want to come to Natasha's pity party?" And then he'd give me the biggest phony smile he could. His behavior was cruel, because he sought only to hurt and provoke me. To this day, I despise him. I learned that I couldn't talk to him about things that bothered me. Even now, it's hard to trust anyone because of similar experiences with him and "men of God." I've also left Christianity.
I ended up being diagnosed with major depressive disorder, to me a natural result of constantly being belittled for having normal human doubts and feelings. Since I could only internalize my feelings, I ended up hating myself for having "sinful" feelings.