I have read that chocolate is bad for dogs, and since the vets say that, I am sure that it must be true. This is something that has come out not that long ago; but it was not known at the time I was growing up back in the 1950's.
I can't remember when I first read this; but I think it was in the last 10-20 years.
Before that, people always gave chocolate to their dogs.
We didn't give them very much chocolate, but all dogs loved sharing a candy bar with their owner; and pretty much, the dog owners like sharing their Hersheys bar or Three Musketeers with their dogs, too.
Chipper's very favorite was M&M's. Any time we had those, he would sit right there and wait for his turn for an M&M.
Of course, eventually, I read that chocolate was not good for a dog, and stopped giving him any M&M's; but I still share bites of my chocolate muffin when I happen to have one along with my breakfast coffee.
Maybe it is because people never gave their dogs very much chocolate that it was fine all of those years. I don't know.
I just know that everyone did, and our dogs didn't ever get sick from it.