To be honest, I found Gyrre's comment confusing, but I agree with Farideh anyway.
Sorry, I made that on the last break of a 12 hour shift ([sarcasm] yay holiday schedules).
The mom in that last panel didn't explain the 'why' to her son[1], so her reasoning was ambiguous [2]. The second part was a very rambly way of me saying I still don't understand a large chunk of what normies consider 'rude'[3]. In my own personal experience, sometimes the 'rude' thing makes someone uncomfortable (like if it makes them confront their own mortality). Accomodation stuff usually makes sense but admittedly has to be pointed out sometimes[4].
[1] a common parenting mistake my generation experienced
[2] I know it was a setup for the postscript joke.
[3] Things that are inconsiderate or a matter of personal safety (like not outting someone) are easy to grok as being rude so long as I'm not too stuck in my own head that day.
[4] Only recently learned about the fake movie tumblr users are creating called Goncharov, and saw a post requesting that posts for it be tagged with 'unreality'
for the sake of users with psychosis.
EDIT fixing formatting