Letting them call it a 'Preferred' pronoun allows them to seem 'polite'.
Forcing them to use the term 'Mandatory' shines a light on the power play.
Force them to use the correct term.
"Oh, are you suggesting that you have the right to issue a MANDATORY pronoun?"
I have one pronoun for everyone of the 85 genders, the queers, the faggots, the bull dykes, the tranny pedovores. And that is FUCK OFF AND DIE.