Saying it's grammar and you can't use bad grammar is a rationalization -- grammar's also an entirely invented thing and it changes over time and if it changes now because we're all getting on board with NB folks existing, then that's just one of a million grammar changes in the 2010s.
Saying we have other words and they should be happy we're using other words is just a rationalization -- it's their call to make and we can either let them own that or we can keep insisting NB folks don't get that self-determination.
"Neat," right???