Frankly at this point you aren't practicing self defense. Your sister is in a horrible situation that she created for herself, and she needs help because she's self-destructive and you're not helping her. And you are letting this person who you know is a danger into your house? I tell people all the time: If you're in a bar and someone gets in a fight, that isn't self defense. You go to bars so that you can get in fights. If someone starts a fight when you're there, it has all the validity to me of saying "I flipped this guy the bird and called him horrible names, but when he attacked me I was so surprised! It was self defense!" Personally i'd disown my sister over this until she came to her senses.. probably after being found half dead in a basement or something two or three times, but if she choses to do that to herself, I don't want her anywhere near me. That said, the whole 'nonviolence' thing is overrated when dealing with ferals who can't comprehend anything beyond instant gratification of anger; this man certainly sounds like one. Yea, i know exaclty what you meant. But you never know the whole story either you know what i mean?