How can I tell my child that he is stupid in a way he can understand?

Please help. My little boy is driving me crazy. Obviously, I love hm and all, but he is soooo stupid! All he does is crawl around on the floor, and spout little half words like ba-ba, or da-da. I tried screaming at him over and over again, "You're stupid! You're a stupid baby!!!!" Is there an easier way to communicate this?