RMS's stance is that "they" is not a grammatically valid singular pronoun, so he'll not use it.

If somebody told you that their preferred pronoun was "we", I doubt you'd use it.

> not every transgender person wants to be thrown into an "other" category with their pronouns

RMS's pronoun "perse" is gender-neutral (not non-gender).

The stance is IMO crazy, but he does have a point that using "they" as both singular and plural introduces ambiguity.