When someone doesn’t want to be called “it”, because of how dehumanizing that is, and you call them it anyway, it contributes to the dismissal of non-cis identities, and their continued dehumanization in many levels of society. No calling me that won’t make me kill myself, but it’s still really harmful language and I’m just expressing that in hopes that someone here will know how harmful that language can be, and will keep it in mind.
He/She is fine.