Hot peppers are not mentioned in the article. I found no credible article that mentions peppers. If was really bad both my dogs would have been ill! I think this article is hyperbole. Even though they seem to be a vet, it's really overstated. It takes a little bit of scientific insight and blows it way out of proportion. Most of the info posted on the Internet is actually that - regurgitated nonsense. When I look into the research, a dog would have to eat at least 0.5 percent of it's weight in onions to be noticeable - not yet 'toxic', and much more than this to be a problem, and then lots more to be fatal. That would be a huge amount for my dog, who incidentally doesn't like onions near her - they are a repellent to her! Go to a reputable vet-centric site. I like the humane society one
http://www.humanesociety.org/animals/resources/tips/foods_poisonous_to_pets.html . This one is pretty good too
http://www.petpoisonhelpline.com/poisons/
Some of these are true for people too. Most of these foods are more in the don't-eat-excessive-amounts category. Even most vets are not very knowledgeable about this. I have a friend who's a veterinary toxicologist (pathologist too), and she say's most of these issues are not really a problem. The exceptions exist. I do not feed my dog chocolate, or onions. I've looked into the grape issue and read the scientific papers and it's scary. But there are dogs who eat them all the time, all their lives with no problems - and it's still a mystery. But I don't take cooked onions out of something she may eat a little of. She's eaten a bit of chocolate too (Kid's gave it to her before I could stop it), but she would have to eat pounds of it to be a problem as she's pretty big. She doesn't get much people food period. And she doesn't get into things - she's very obedient. My first dog used to eat hot pepper sauce on chips, shake his head, and want to eat more. But I never gave him much (only a few chips - with a few drops of habanero sauce), and only a couple times in his whole life. He never tried to eat hot pepper plants. My current dog does not like hot peppers (well if there is a little salsa on something she will still eat it), and does not really like chips. Oh, and onions, they would work as an anti-dog application for her too. Would not eat them, especially raw.
I never worry much about these things as my dogs never really liked anything but meaty foods. You might try lemon oil - squeeze it from the skin of a lemon (not furniture polish!), my dogs have hated this smell. Or tell the dog NO, give a little tap on the nose, look them in the eyes, say no again, and make them lay down. This usually works eventually.
Also, hot pepper plants even though in the nightshade family, are edible. They are commonly used in Korea - to make a namul dish.