“Cisgender” is no more a derogatory term than “heterosexual.” It’s simply a descriptor. It means your gender and biological sex are the same. That’s all.

It’s only derogatory to you if you feel that “cisgender” should be “normal” and thus not have a word. But we have a word for all kinds of things people might consider “normal.” Sighted is a word even though being able to see is the norm. I’m sure you can use ‘sighted’ in a derogatory way. Maybe some blind people even do, I don’t know. That doesn’t make the word derogatory.

“Cisgender” is not the queer equivalent of something like “tranny.”