Consider viewing it from the child's perspective. It sounds like he is really sensitive to praise and disapproval. According to child expert Aletha Solter, Ph.D., "From the baby's point of view, it is better not to defecate at all, rather than to risk defecating in the wrong place." She also says it takes most babies weeks to learn toilet training given they have the muscles developed (involved in urinating & defecating) and bladder must be a certain size (so he's not going less than every few hours). Emotional requirements include being willing to take on the responsibility. "Sometimes toddlers are busy perfecting other skills, or their attention is preoccupied by stress," says Dr. Solter. She recommends you trust your Little Man and be very patient with him. "The best approach is one that is relaxed, fun, non-judgmental, and matter-of-fact . . . . The less you push him, the quicker he will do it, and the better he will feel about himself." She suggests you use "play therapy" to help him have less fear about using the toilet. Example she suggests:

"Give your child some brown play-dough (to represent feces), a doll, and a small potty, and encourage free play while you pay attention and observe. You can also contribute to the play by pretneding that the doll is afraid of the potty. If you can get your child to laugh, this will allow him to release his anxiety and tension."

from THE AWARE BABY by Dr. Solter