The essay - Objections to ‘Cis’ - by Helen Saxby from 2020 expresses the views of a lot of women I know. Some excerpts, with some edits of my own added:
Cis is short for cisgendered, and the usual definition (apart from ‘not trans’) is having ‘a gender identity which matches your sex assigned at birth’. Immediately there are two major assumptions to challenge: sex is not ‘assigned’ at birth, it is recorded, and 'gender identity' is a concept which is rejected by many people and is in any case impossible to define.
Calling me cisgender does not just say I am someone who is ‘not trans’, it ties me in to a faith-based belief system I don’t share and which I see as actively harmful, especially to women and girls. This is a perfectly understandable reason to reject the word ‘cis’ and that should be the end of it… but there’s more.
The unwanted labelling of ‘cis’ is enforced whether you like it or not. Many women object to being demoted to a subset of their own sex class, when previously the word ‘woman’ was sufficient and carried meaning.
Although today's transgender movement is dedicated to the idea of always believing that people are exactly what they say they are, there's a notable lack of acceptance of the positions "I’m not cis" and "I don't have a gender identity." According to the ideology, everyone has a gender identity and if you don't identify as trans or as another special identity like non-binary or genderqueer, it means you're cis.
This imposition of a gender identity onto everyone - and the insistence that gender identity is a core component of self and a defining characteristic of everyone, even those who say they don't have a gender identity - is one of the things that is most regressive about trans ideology. I didn’t spend a lifetime trying to escape the confines of the feminine gender box only to be forced into the restrictive cisgender box instead.
But there are worse problems with this terminology than that.
If you're forced to accept the word ‘cis’ then you're essentially conceding that women come in both male and female varieties. ‘Cis’ is the other side of the coin to the ‘transwomen are women’ mantra, in that it ensures the category of women contains both sexes.
In this system a ‘transwoman’ is a male woman and a ‘cis woman’ is a female woman, and these are now equal subsets of the category ‘woman’. Cis is doing the job of letting men into the female sex class, and it means you can no longer be just a woman, you have to make a choice over what sex of woman you are.
when women express fear and discomfort about males invading our spaces and sports, we are told it's silly and wrong to worry because the males coming in are "trans" rather than "cis"- and supposedly only cis males pose a problem.
Cis works here to differentiate between the men who are really male (cis men) and those who are really female (transwomen). At the same time it puts ‘transwomen’ and women into the same exact category.
In accepting the word ‘cis’ you have lost the means to differentiate between men and women, because they both now come in both sexes.
Once ‘cis’ has done its job of mixing up the sexes into a new gender-determined classification, a much bigger problem becomes clear. The two subsets of women (cis and trans) turn out to be not so equal after all.
Cis is being used to posit an axis of oppression which subverts the usual order of things and places females as the oppressors of males: if women come in both cis and trans varieties it’s the cis ones who have the privilege. Cis privilege means that cis people oppress trans people, so it naturally follows that males are the most oppressed of all women.
Once that’s established, then it’s clear that female girls and women, with all our supposed "cis privilege," can no longer be allowed to organise, engage in activities, or have spaces and services on our own without our male ‘sisters’ being included. Women and girls who are female can never have anything just for ourselves ever again.
The result is that women and girls are increasingly being castigated as transphobic, bigoted and exclusionary when we prioritise females and don't include males in activities which were formerly perfectly well-understood as female-only. Endeavors, facilties, services and safeguarding protections that once would have been celebrated as progressive for centering women and girls, helping to promote justice, leveling the playing field, providing balance to correct the male default, are now hateful signs of ‘transphobia’.
It’s a double bind: we are apparently expected to adopt the categorisation of ‘cis women’, but then we are not allowed to organise as ‘cis women’. Everything we do must include 'trans women' aka men.