Here's an idea:

If # of people accepting a term to describe themselves > # of people using it to describe other people, then it's not a slur.

If more people foist it on others than use it on themselves, then it's a slur.

Insults should not be banned

I have seen "cisgender" used as an insult a fair few times

That doesn't mean that "cisgender" 'is' an insult all of the times

Ppl who don't want to be labelled "him" or "her" should respect other's wishes not to be labelled "cisgender"

And vice versa

Life is often a choice between live and let live

Or stomping on toes

Most ppl who choose the latter think they'll be the only ones doing the stomping

Which becomes a cycle of playing stupid games and winning stupid prizes