As I said in the post, any word (including "cis") will be insulting if it's used insultingly, and indeed some words are always used that way, "honkie" being one such. Anyone's entitled to object to being insulted.

Objecting to being accurately described is a slightly different matter. I don't mind so much about the word "cis" in itself: if an alternative gains wider acceptance that's fine with me. I don't however think that it's reasonable to say that it's insulting even to have a word - any word - to refer to a particular group. That's the belief that seems to lie at the bottom of this: "We don't need a name, because we're normal."