I'm trying to imagine the type of personality it would take to look at a cute, cuddly, soft, warm, fuzzy, happy creature... any creature, and be able to just destroy that animal without a care. This is a dangerous personality, the kind that would also feel no remorse when killing a human being, and that is probably the next step for a lot of people who start out by poisoning a poor little dog. Where I came from, stray cats were and still are a huge problem... not so much for dogs for some reason, but people don't seem to have any concern whatsoever when they hit a cat on the highway. In fact, I'm pretty certain some of those cats get hit because the drivers swerve to make sure they hit them. It's so sad, but you can't do a blasted thing about it, except try really hard to help stop the animal abandonment issue that causes all the strays in the first place.
I agree that dogs should be kept where strangers can't get at them as people are real horrible sometimes. I've seen the results when wild animals have died from poisoning and it's definitely not a pretty sight. It would be devastating to see those same symptoms in a treasured family pet, especially one who was perfectly healthy just the day before. In the past I always had outdoor dogs, large animals with thick, long hair who didn't especially like being cooped up inside where they found it too warm. But I never worried about people coming into our back yard and harming our dogs... that just wasn't common-place where I grew up. Today, I think all pets should be kept indoors as much as they can tolerate, it's just not safe out there anymore.