My wife told one my nephews who kept making disparaging comments at the tv “cut that shit out. In this house everyone is allowed to be the way they are”.
I think that’s a useful model for this conversation.
Yes, the difference is that this is aunt to nephew in aunt’s house. There is a definite power differential at work there, so all that’s left to do is to set the norm in a clear but respectful way.
If you don’t have that, and they don’t want to listen, then it’s hard to get through. Things are necessarily going to get either a lot more protracted or a lot less friendly.
I'm prepared to lose contact with people that are problematic or toxic, especially those with the more radical views, but it's not nice to watch someone I've known for many years gradually lose all their friends for similar reasons.