Size really does not matter. Dallas was a 75 pound husky and Missie weighed 9 pounds. Dallas was aggressive but she learned she was not allowed on the couch and Missie was. Same with the bed, Missy slept with us and Dallas slept on the floor. It is all in the way you train them. If you are concerned, I would be talking to my Vet or a reputable dog trainer.
The more I get to know people, the more I love my dog...
There ain't no cure for stupid ...... but we should make sure we laugh and point it out to everyone else