Who the hell would think "oh no, there's someone across the globe that might have a hurt feeling if they knew about this private conversation"?
I'm pretty sure they were trying to say that continuing to normalize it is a bad thing because it says to the other people in those private conversations "these are acceptable things to say to and about others".
I think it's kinda like how some people would argue it's bad to say racial slurs, even in private conversations, because it can be a signal that racism itself is acceptable. It's similar with anti-queer slurs too. The mindset is that it's better to avoid using a person's body as the basis for insults.
Like, I'm trans, and when I was still hiding that fact from others, I heard lots of slurs and hurtful things, because the other person in those private conversations thought I was "one of the guys". It'd be nice if more people who are not the object of mockery would confront it instead of going along with it.
Anyway, I think that's what they were saying, and I hope I've made sense.