Need help with this ?

cause some people are evil

Some parents think it's a way of disciplining their child. They don't realize they're abusing them. It happens sometimes when the parents are also being abused during their childhood and what they've experienced they  do it with their children.

Thanks for an excellent question and the answer boils down to the fact that the parents were abused and neglected as children and thus, they have not learned good parenting skills and worse yet, they don't think they are doing anything wrong.  After all, their parents did it to them, right?  So, it must be normal, right?

Yet, after they abuse, they are fearful that other people will find out what they've done.  And when their child confronts them, they threaten the child with more violence, make excuses, tell the child they deserved it and it wasn't as bad as the child thinks (knows) it was.

they mightve learned it from their parents 

Lack of education, frustration, no emotional support.