What did Paul say about juding those outside?
What did Jesus say about juding at all?
Sorry to read that, mate. It sucks.
I decided last year to always be nice and friendly to JW family even though they treat me like shit. Get on with living a good and decent life and always be there if/when those people leave themselves. I dont talk about religion at all to people who do (very rarely) talk to me. And I even sent non-xmas presents to my neices and nephew in December. One sister returned them to me, the other accepted them and thanked me.
That's all you can do in this situation, take the high ground and be the kind one. I'd either ignore it or reply with a lovely loving letter signing off with "I love you no matter what religion you are".