How is something "officially" a slur? Who is the governing body for slurs?

Do you feel this way about calling someone a dick? By your own definition, it's a slur towards men.

Cunt is no different, it's just yet another way to call someone an asshole, it's barely a gendered term anymore. If you'd have brought this up back in the 90's, you may have had a point, but it really isn't commonly used as a slur against women anymore. That's what differentiates it from the other terms of unendearment that you listed.