I understand your DH's view, and yours! It's so difficult and exhausting when the narrow-minded dominate the airwaves with their nasty, scoffing prejudices against anyone not exactly like them.
And everything is still so raw after Thursday. But they're family and presumably they love you.
When you see them, can you have a firm word and put political and social topics on the banned list?
As in, GF, you're coming to our house to celebrate the birth of a poverty-stricken middle-eastern baby who spent his early childhood as an unwelcome refugee in a neighbouring country being a burden on the economy, (the flight into Egypt) and grew up to be such a thorn in the side of the establishment that he ended up executed.
If you are tempted to mention politics or utter judgements on people you don't know, you will make everyone uncomfortable and yourself very unwelcome. Can you undertake to bridle your tongue, get out of the seat of the mockers and scoffers (see Psalm 1) and keep the conversation on pleasant, positive topics?"
You don't need him to try, you need him to do it. Your DGM, too. Why not get them to watch each other?
If they slip, "You're on thin ice there, time to turn the conversation!"
And if a rant begins or BJ's name is mentioned, everyone needs to get up in a body and leave the ranter alone in the room for five minutes, even if it means leaving the table during a meal!
You can do this. I don't believe ranters even enjoy it much; it's just a bad habit. Habits can be broken.