I don't think not knowing what breed a dog is or that they come in that color makes someone stupid or a moron, but there are people that come off that way, not by not knowing, but by other things like arguing about the breed because they don't believe they can be that color. Alot of people tell me they've never seen a white. I've never actually had anyone argue w/ me, although I've gotten the impression that some may have thought I'd been taken, but only when mine were puppies, most recognize them as danes, or ask and have no prob excepting the answer.
I'm generally very nice to everyone that wants to talk dogs w/ me, and it doesn't matter what they know or don't know. But I have encountered a few snotty people, generally it's the "my dog's bigger then your dog people" and even then I try to be polite.
There do seem to be alot of dane people that are really touchy and get really snotty about some of the everyday things dane owners hear "do you have a saddle for that thing?" "Wow, couldn't you find a big dog", etc, you understand. For them they may not see one everyday and think they are being clever, for dane owners they often hear these things several times a day. It comes w/ owning a dane, and if it's such a horrible experience they should have chosen a different breed. I don't care if it's the 100th time I've heard it that day, I always smile politely and joke back or nod at them, or whatever. Sometimes I worry these people give dane owners a bad name, but I promise we're mostly really nice people! I realize that is probably not the case in this situation, sounds like this guy was really in the wrong (I wonder if he really thinks that, maybe when he got home he did alittle reseach and now really feels silly, I know that's what I would have done, but there is a good chance he will always think he was right and nothing will change his mind).
I guess that's off topic, but all part of the joys of dane ownership!
Now 'I' did once ask a dane rescue what their puppies were mixed with! I could clearly see they were not pure danes, but the woman seemed really offended and informed me that they were all dane! I didn't argue, just told her they were really cute, I wasn't looking to upset anyone, if I'd known they thought they were pure dane I probably wouldn't have said anything, I did sort of wonder what their story was, but never found out.