Don't really care one way or the other. It's a word, used to define a broad cross section of humanity, just like dozens of other words that people use.
Some people are offended by it, some aren't, just like dozens of others. Considering I've had gay friends, and random people on the internet, tell me that the following words are both offensive, and also the correct term for describing a homosexual, I just chalk it up to "Nobody can really figure out one damn word to define anyone".
Queer
Fag
Gay
All 3 of these are apparently simultaneously offensive, and also "the right term to use to describe us", that I've just given up bothering one way or the other. Call yourselves whatever the fuck you want, call me whatever the fuck you want. I don't associate anything negative to cisgender at all, it's just a word used to try and define me. So knock yourself out, call me cis all you want, until you decide to call me something else. I really don't give a damn.
Also, I've never seen the word used in a direct insult phrase, like "You damn cis!" "Stupid cisgender!" like I've seen the same phrases, but with fag or queer replaced, so saying it's an insult seems odd to me. It's all about context, and in my experience, the context of using the word itself, is simply a descriptor. I've seen plenty of people use the word in insulting statements, that are blanket declaration of behavior. "All you cisgenders act like it's all about you, none of you care about anybody elses problems. You have no idea what our lives are like" But to me, the context of that insulting statement has nothing to do with the word "cisgender". It would be equally insulting if they used "heterosexual" or "straight". So again, the word itself doesn't bother me. It's the potential asshole using the word that I have an issue with.