You dog does not have to be threatening. Your dog can be by your front door. It is not barking or growling. It is doing nothing more than sitting. A human can report your dog as being threatening and you will be found guilty of having a dangerous dog. This person can have an unrealistic fear of dogs and make the report. The person can firmly believe that any or every dog is dangerous and believe in their heart they are doing the right thing by reporting your innocent dog. It can be that the person does not like you  even if they have no reason not to like you and they report your dog.