Describing cis as a slur is... Wow.
It's a slur.
I can tell you from personal experience that this says more about you than the word.
The majority of people in my circle would self describe as cis, and most people I interact with would self identify as cis if the meaning was explained to them.
Backhanded insults like this won't convince me that I'm wrong. On the contrary, it shows me that you do intend to insult and that the word is in fact a slur.
- Add an unnecessarily complex psuedo-intellectual layer to the discussion in order to catch normal people off guard and make them feel "uneducated" so that they can be "educated".
- Decouple the idea of normal from heterosexuality, which is, frankly, normal due to it being the most common state for of existence for people.
Overall it is a purposeful attack on the status quo. In summary, "cis" as a term is unnecessary.
Um, no, other than arguably being wrong on the broad kind of motivation in either case, you seem to have also confused the word “cisgender” (or “cis” for short) with the word “heterosexual”.
Transgender people can be heterosexual or homosexual or asexual or any other sexuality, and the same is true of cisgender people; having a term to refer to people who do not deviate from the until-recently-in-our-society culturally obligatory stereotypical relation of gender identity and sex characteristics at birth does nothing to reduce heteronormativity of language compared to just referring to them as “normal” (and then, depending on context, elaborating further on the axis of normality and possibly whose norms are being referenced), to the extent that having a word does that, its the word for people who don’t deviate from the until-recently-in-our-society culturally obligatory stereotype of sexual preference for partner gender based on their own gender.
But, independent of undermining the norms involved, its sometimes useful to be have a convenient concise term, which both “cisgender” and “heterosexual”, in their respective domains, provide.