Mean dogs

Jake walked up to a dog the other day while we were out and started petting it. I've been trying to explain to him that not all dogs are nice dogs like Stetson and that he can't just walk up to random dogs and pet them. I wasn't sure if I was getting through to him or not until he woke up last night having a nightmare that some mean dogs were attacking him. Maybe I should back off on the mean dogs for a while!!!!