You get right down to it, a cat is like a 20 watt bulb in a brown-out. Some are pretty smart at being cats, it's the rest of it that gives them trouble.
Cats are also conservative in the extreme. They like "going" in places they've "gone" before. In other words, if it smells like the place they last "went", they're gonna do it there again. And cats have far better noses than we do. so an item can smell clean to use, and still smell like an outhouse to a cat.
So when a cat uses your favorite shirt as a lavatory, you have to use a good stain remover, wash it thoroughly, then use a strong disinfectant on it. If that don't work, check with your local petshop for something you can use to keep the cat away from the item.
The best way of ensuring the beast doesn't use your laundry as a toilet is to keep his litter box clean. I know it's a hassle, but as soon as he's done his duty, you get to do yours. Cats aint as low maintenance as some would have you think.
BTW, you can consider his actions something of a compliment. He trusts you. If it smells like you it must be a safe place, and cats prefer doing their business in a safe place.
Now do you understand what I mean when I call them, "silly beasts"?
