I have a similar problem. Bentley hides under my legs when confronted by both large and small dogs, even if the other dog was quiet. He came from a big family of Yorkies. His siblings would play with each other and try to include him but he would stay away from them, go by the corner of the play pen and just watch. We are scheduled for a puppy play date with my friend's chihuahuas soon.
Its weird cause he runs away from dogs smaller than him but he growls at and attacks cats that are bigger than him.
__________________ Cheers! 
Bentley and his mom |