My daughter-in-law constantly shouts at my grandson

My daughter in law is constantly shouting at my grandson and I dont think it is necessary all the time. But if I ever tell her that, she feels bad and complains to my son. My son never listens to my side of it, but just requests me to stay put of it.

How do I explain to him that it is not okay to shout at children for everything. It will only end up spoiling them because they will not know when they have done something really wrong if they are so used to being shouted at.