If you take out the queer theory aspect, this is basically a conversation about endonyms (names people apply to themselves) vs exonyms (names others apply to them).

For example: Deutschland is an endonym. Germany is an exonym.

Exonyms aren't defacto offensive, but they're often considered less respectful than endonyms.

We're talking about a specific subset of exonyms here: words that don't refer to a specific group of people, but refer to everyone except us. It's not about what someone is, it's about what someone is not. Maybe there's a term for such words, but I can't think of it right now, so I'm gonna call it a "complement" (as in set theory). Examples of such words include: "gentile" (not Jewish), "gadjo" (not Romani), "hearing" (not Deaf). Hearing people tend not to call themselves hearing, or think of themselves as hearing. But it is a relevant term for deaf people to use among themselves. Arguably, "straight" is such a word too—I don't think most straight people really think of themselves as such, but it can be a useful term for us.

I think the real difference between cis and those words is that "cis" isn't defined as "not trans". It's defined as "identifying with your real sex and its gender stereotypes" or whatever. If it just meant "not trans" I wouldn't mind much.

Would they still use it derogatory in jokes sometimes? Yes. But I'll be the first to admit I've made a few jokes about straight people in my time, and it was just a joke, I didn't actually mean it.

What really bothers me about cis is that they presume to know how we think or understand ourselves, and refuse to listen when we say "actually no one thinks like that."