I don't think people are ' strange' ratter- I think they are drawing from their own experience. We all know that chocolate is poisonous to dogs, but to most of the dog owning community this is recent knowledge ( the last 20 years or so)- before that it was a routine treat for a huge number of dogs. Certainly when I was a kid in the 60's I used to buy my dog a bar of chocolate everytime I had one - and the old cliche ' never hurt her' proved true in that case.
Obviously I wouldn't do it now, and niether would anyone else I know, but it doesn't stop the anecdotal stories of dogs which have survived a lifetime of chocolate unscathed.
One could say the same about alcohol and people.