This is additional context from the previous posts. I would agree that such usage in this context is weird and offputting, possibly even offensive depending on the tone. Of course, I would further argue that it's less "cis" you should find offensive than the general derogatory context. As in, if anyone I didn't know started talking about me across the room as "he's just a XXXX, what do you expect", it would be offputting, but it really wouldn't matter to me if XXXX represented "cis", "hetero", "liberal", or virtually any other term.