DISRESPECTFUL ADULT CHILDREN?

Might have made my uncle hate me for calling him out on his rudeness with my grandmother...but somebody's gotta say something. Both my uncles live with my grandparents and have terrible mental health and drug/alcohol problems AND are absolutely disgustingly RUDE! No appreciation for anything or anyone. It breaks my heart and my grandparents just arnt assertive enough to call them out on their BS and deal with it. I don't want to see them being bullied, I don't want to see my nanny's self esteem shatter-but I do every time I'm there. Please friends I could really use some advice on this one...do I try and help? Is there any way to help people who just don't want it? Can my grandparents sanity be saved? How do you deal with adult kids?