Some people just don't get it.
Some people think it's cute when their yap dogs yap at big dogs, day in, day out. Those are challenges for a fight. Fighting words, in dogspeak.
Chihuahuas, Yorkies, Toy Poodles, etc. are always barking off more than they can bite. When they end up on the wrong end of the tooth, it's often the fault of the owner of the poorly behaved, smaller dog.
If people want a lap rat, they should get a real one, or show enough discipline to muzzle their yappy little canine imitation.