Yeah hi, moth balls and chocolate can kill or seriously injure a cat. Showing him the poo, yelling at him and crating him isn't going to do a damn bit of good. He knows the poo is there, and doesn't get why you're yelling at him after the fact. Cats are not dogs and do not respond to crating.
First of all, if the box is clean and you haven't changed cat litter, the first thing to consider is whether there is a medical problem that is causing your cat to have problems. A trip to the vet would be a good idea. Clean the area where he's been pooping with something designed to eliminate smells entirely,
like this stuff. FHwku's idea of moving the litter box to that corner is a good one -- if your cat wants to poop there, why not let him for a while. Maybe the litter box is too far away and he has a hard time getting there, so a second litter box might be helpful.
It might be a good idea to read some books about cat behavior, so you have a better understanding of cats. I don't mean to sound harsh, but honestly, if you're as angry as you seem about this, maybe having a cat isn't for you.