What stops you from telling them how you feel? I woulda told the uncle to feck off a longgg time ago, sorry but I would....Why should you have respect for them if they have none for you...
Saying that, that's not detaching, that's reacting...
I find it quite easy to detach when I know what they're saying is BS, when it's untrue, when you don't care what they say....
If he/they start, just walk out of th room, don't dignify their remarks with a response, don't sit there and take it, just stand up and leave the room.
I'm sure others will have better advice....