This slows down the motor activity and increases the time the water takes to make it through the funnel. This challenges the child's self control and increases the child's concentration. It sounds like it's conference time with the parents and the cause of this child's anger be identified. Also, please look at nutrition. I love conferring with parents of children who are exhibiting unusual emotional responses to seemingly simple social situations.
Conferences are usually quite reflective and insightful.
If the child has a sibling who is unusually rough with him, this needs to stop. Toddlers are emotional and physical sponges. They become their environment. There is a child in my class who is extremely rough with his friends. I find that if my assistants and I continually demonstrate gentle touch to him, by example he learns.