Dogs of all breeds and mixes will most certainly eat things that are toxic to them. I am not sure what universe someone is from that doesn't know this, but just in case anyone here believes this dangerous nonsense, please don't assume your dog knows what is poison or not. Over 100,000 dogs are poisoned each year from everything from yard chemicals, flea/tick treatments, to-- yes-- thing they eat.
Dog eat toxic food every day, and die often. Chocolate, raisins, rat poison, even freaking old fashion car antifreeze, avocados, cigarettes, caffeine, owners medicine left out, artificially sweetened candies (xylitol).
As for milk or dark chocolate, neither is safe, but please read and don't accept misinformation there either.
""Cocoa, cooking chocolate and dark chocolate contain the highest levels, while milk chocolate and white chocolate have the lowest. ... The high level of theobromine in dark chocolate means it takes only a very small amount to poison a dog. Less than an ounce of dark chocolate may be enough to poison a 44-pound dog.""