He is being possessive/guarding his human and you need to stop this behavior or it will escalate. My suggestion would be to put him on the floor when he is behaving this way and tell him no or redirect him. If he was a larger dog it would not be acceptable, so he should not get a pass because he is a cute little 2 lb Yorkie.
__________________ “Never argue with a fool, onlookers may not be able to tell the difference.”  Mark Twain |