You gotta teach a dog who is the boss in the house and sadly enough if kicking it real hard gets him/her to obey you and stop biting your hand off, its justified.

My buddy from woodstock owns Jules Santanas pit Eve now (long story but he really does have it) and if she goes to attack another dog Judd the owner kicks her in hind legs. Its not dog abuse, if your dog is killing another dog, you the owner need to take charge and stop it. Not nessacery kill it, but if a nice bruise is the only thing its going to stop the dog from biting and killing... its harsh but needed.