Is it true that divorced parents have to agree child to see…

Please call me

My grandson got into a little trouble at school regarding homework. The teacher contacted my daughter and she called her ex husband to share what had happened. She and my grandson were on speaker phone. When the ex husband heard what happened he went off on my grandson calling him a failure and if he didn't smarten up he didn't have to come over to his house anymore. My grandson is only 9 years old and thinks the world if his dad. My grandson got so angry that popped blood vessels in his face an crumpled up the hat he was wearing and threw it and had tears running down his cheeks. His father was using himself as a weapon, threatening to remove himself from the boys life. He carried on with some other insults and said good bye. My daughter heard every word and had to calm him down and reinforced that he was not a failure and if he didn't want to go to his dad's after school the next day it was up to him. He was crying and deeply hurt and decided to go to his dad's the next day..
My daughter received a call from my grandson shortly after he would have gotten off the bus. He was crying and really upset and said his dad called her a failure and that gramma and gramps were failures too. He told her that yelled back at his dad that we were not failures because he loves us all very much. Just then his dad caught him on the phone and grabbed it away from him. He spoke to my daughter and said he was taking care of the situation thinking that she would agree with him. She became very upset and told him the ways he was treating their son was emotional abuse and she did not want their son to be brought up the way he was. The threat of abandonment is very cruel. She also said that she would come and pick him up and spoke to their son again and told him that as well. My grandson said it was okay and my daughter said she would call him again later.
About an hour later my grandson called his mom and said that he was okay in his normal voice. He then asked if she was going to take his dad to court. Why would a 9 year old ask a question like that? That had to have come from a talk with his dad. I can only imagine that conversation.
I told my daughter that I can't believe she can't do anything about emotional abuse. If it was physical abuse the police would be called and there would be charges. This is why I ask the question. She said that both parents have to agree on counselling for this young boy. There is also my grand daughter who will be turning 12 in a couple days and she has already asked my daughter if she can talk to someone.
This really hurts her extremely because these are the same kind of things he said to her when the were married. He abused her phycologically and emotionally that her self esteem was is the trash and nothing was ever good enough. She doesn't want her kids to go through that too. Please help. These kids deserve better then this.
They are also not allowed to talk about anything that happens at their dad's house. They told me that a long time ago.

i just wanted to add that our grandchildren do talk to us grandparents very openly and ask us not to tell Mommy. We do share with their Mom but she is unable to act on anything for fear of getting them into trouble. This episode that happened recently was witnessed by her so she needs guidence as to to proceed if there is a way to get around this.