I think it depends on the size of the ears and how they lay. It would bother me too if someone asked me that. It is not that I wouldn't love a mixed breed because I have had them and loved them. It is because we respect and love our dog's so much that it does appear insulting. Like someone who asks if your child is a boy or girl. Your dog has very intelligent looking eyes. I bet that most people know he is a doberman though. My Mako has natural ears, I don't recall anyone asking what breed she was, except as a puppy. Mako has shorter ears, maybe that is why.