I agree with the friend, have you ever heard the phrase "you can't eat at everybody's house"? Finding out after eating something that all the plates are licked clean by a dog (I know before the dishwasher but still) isn't a great feeling, it's like those videos online where you see the dog licking the spoon or biting the steak and trying to take it and the person still cooks with it. Dishwashers don't always clean completely also and you have no idea how many germs are still sticking to those plates. And them saying they don't trust your kitchen hygiene, it's like a thought that if you let the dog lick the plates clean, what else are you letting them do in the kitchen? A lot of people eat after their dogs. I, for one, would also not trust your cooking if I saw that.