C.L.
You are not going to be able to help him unless he wants help. He is expressing himself how he has learned to growing up and fortunately parenting techniques have changed 100 fold since he was a child. Why don't you check into getting both of you into a Love and Logic parenting class (so he has support and you know what he is learning) and see if that helps put some different spins on how he deals with the children. Unfortunately, they are not only upset by his actions-they are learning how to act from him and you really need to get this fixed now before you have much bigger behavioral problems (from them OR him).
Good luck and let us know how you fare.
C.