Personally, for me it’s the idea that just because you don’t experience something (dysphoria, or being a gender other than what society expects of you) that doesn’t mean those experiences aren’t valid.
I get sooo tired of the response “I just don’t understand! I love being my AGAB! Why can’t you just get over it?”
Real answer: that everyone is entitled to bodily autonomy, and being autistic or bipolar or having whatever other neurodivergence doesn’t mean someone can’t also be trans.
Pet peeve answer: that cis is not an acronym and shouldn’t be capitalized.