I imagined that the people are posting on the sons FB page which is not the open forum that we have on Topix. And as such I would imagine that those people felt a little more insulated from the random snark of unknown posters (the mother).
I would liken it to the mother showing up at a party the son was hosting, and her proceeding to preach to his guests about their life choices and sexual orientations. Some guests may have come dressed in drag because they did not expect someone to start preaching to them at his house.
But as I said... No clue how FB works.
I re-read the original letter. LW's mom was arguing with LW's friends about their lifestyles presumably from things she read on FB . If it was LW who has been confiding in his mom, he should STFU. If mom has just been responding to other people's FB postings, he has no gripes.
1. He can unfriend her
2. his friends are big boys/girls. If they don't want to be harangued they should unfriend mom, delete her posts or not post stuff in public.
3. Public conduct begets public comment, something my elder girl learned in 3rd grade.
4. LW is not responsible for his mother and his mother is not responsible for him. Think of her as a blathering former manager .
FWIW, the older generation that is new to the i-net has less inhibitions and tact and hasn't figured out that whatever you post or send lasts forever and on a well lighted billboard. BUT, this group is now in their late 60's. Everyone else who has been working already "knows" this.