If I prefer not to be called that, then yes it is. I believe that's the right they're asking for.
Not really. If "cis" correlated with trauma and you went out of your way, without argumentation, or twenty-two pages of debate, to respect other peoples' pronouns and the like, then yes, this case could easily be made. But that hasn't really been the case here. If everyone agreed in good faith to respect these things, a) the thread would've been a lot shorter, and then in turn b) people would also be willing to believe that a Latin prefix could in some cases cause people harm.
It's too similar to the height example, for me. And notably, simply referring to someone as a trans person (assuming they are) is not in of itself offensive. Which means we're really got to do some kind of work here to define cis as one, and given the attempts so far? Let's just say I'm not convinced Berzerker is being entirely serious here
Cis folk, like myself (and others here, I'm sure), are the "norm". That's why cis is being popularised, to stop treating trans folk like a set of "other", or "not normal" people. There is no baggage associated with being called cis. It's a term with very little (historical) cultural baggage. Most weaponised forms of describing trans people don't actually involve the word (or prefix) trans. That's not to say that being labelled as one can't cause harm, and technically the same goes for cis. But only technically, covering every possible semantic eventuality.
The two aren't really comparable; it's like comparing any cultural majority with a related disadvantaged minority and claiming that because the majority can technically be insulted, respect on both sides has to happen for anything positive to happen to said minority. Gay folks before (mainsteam acceptance of) gay right. Black folk. White women before their vote. Slaves. And so on, and so forth. Trans folk are actively marginalised in today's society - us cis folk aren't, simply for being cis. We're seen as "normal", and we aren't so much as even blinked at twice in that regard.