I've been told it's due to it being derogatory to other groups, similar to how using random slurs towards others can still cause discomfort due to association of the malice behind the word's origin.
Knowing different folks can lead to different perspectives, some have a more negative experience with the term typically due to a catch-all use.
But yeah, typically it's the less hassle choice to just say 'futa' to describe fictional non-transitioned charas like the ones in ToA and just assume balls and vag are like weapon attachments
I do appreciate the detail you went into, with your response, since it shows a depth to your understanding and view on the matter
But, tbf, you have nothing on the ol' reliable response to convos like these.
- Hiro's thoughts before entering combat, as he puts on his buttplug and ball-gag to remain a virgin.