Sister in law...should I get involved?

Okay ladies I've got a question for everyone. Honest opinions please.

My sister in law had a boyfriend who on the surface was an okay guy. Then slowly his true personality came out. He is majorly racist...in my own home he said the " N" word. I made it perfectly clear to never say anything like that in my presence cause we are all human.period. He likes to smoke drugs...not just the herbal one and as of today he is an abuser who hit my sister in law and then we found out that he stabbed a guy awhile ago for drug money and was charged. Ya a real winner this guy.

My question. Should I get involved. Helping her out. She will be moving from one city back to our city. I offered to help her pack and be with her just in case this guy comes around. What does everyone think here?