Aw, people make joking comments like that all the time, and it doesn't offend me. I understand why some people don't think they're "real" dogs....and let's face it...even WE don't really think they're dogs!
We think they're HUMAN!
People in my own family (husband and sons) gave me a hard time for wanting a "little rat dog". Until we GOT them!
And now they're the biggest yorkies fans in the world!
I figure, dispairaging comments just spring from the ignorance of the yorkie-uninitiated!