Don't understand

I honestly don't understand how any one can be mean to a child. No matter what age of "how bad" the kid is. A kid is a child of God and should be treated like it! Today in Walmart there was these two girls about the age of 5. The dad sat there and yelled at one of the girls. The poor baby started to cry and it broke my heart completely! The two girls were dirty and it made me sick. The parents both had the "I don't care.. " attitude all over their faces. The little girl looked at me and it was hard to smile at her knowing what she was probably feeling inside. I honesty just want to go over and hold her and comfort her. Don't get me wrong.. I believe in discipline when needed. But I also believe you should do everything in love. The little girl touched something her dad told her not too. He screamed at her hateful. I understand that kids at times can do horrible. But if your horrible to them that's not teaching them anything. I babysit my little cousin. She's 3 now. I love her to the moon and back.(like she says) The other day she hit me. I made her look at me in the eyes and say sorry and told her hitting isn't right. People always say I let her get by with two much. But I love her and feel bad for the poor child. She's bounced away from 4 different houses. Parents aren't together. But I do teach her what's right in wrong. For what she learns now is what she will hold onto. Same with us. What we learn is what we will hold onto. So the question is what are you learning? Is it Christ and living a life like He did? (your answer should be yes!!) 
Okay so I know this post is everywhere here. More of me just going on and on but! There are a few points. 
1:kids are from God. Teach them in the right ways. 
2:it's our job to teach kids. No excuse. 
3: love everyone ! 
4: learn more about God each day 
5:God loves you so much :)