Try shutting up
Well…
It’s not exactly a slur, true, but it is nevertheless highly objectionable, and not just to the person being called it. It assumes matters not in evidence – it assumes that there are “cis” people and “trans people” when in fact there are only people. Cis would not mean anything without the existence of the word “trans” but the word “trans” names something that doesn’t exist. We don’t need the word “cis” because it’s just the equivalent of real or actual or non-fake. Trans women are real, actual, non-fake men. Trans men are real, actual, non-fake women. It’s simpler to just ignore the fakes and go on knowing which people are which sex the way we always have.
“Cis” is not exactly a slur, but it is a specialty word that exists to legitimize the war on women that trans ideology is. No I’m not going to “try this” when the “this” is pretending there are two kinds of women, fake and real.

…thus changing the topic from sex to gender identity, from biological (fe)males to people who think or feel is certain ways best left unspecified, are in possession of an invisible, undetectable, undefinable, indescribable, inexplicable, inscrutable (fe)male soul or essence etc., while at the same time turning the statement into a claim about what’s going on inside other people’s heads. Either that, or “cis women” relate to “trans women” the way fruitbats relate to baseball bats, i.e. not at all, it’s just a bad pun.
Those who identify as trans have tried to impose that ridiculous prefix on us, but the way I see it, people leaving a group to form one of their own are free to call themselves whatever they wish, but they don’t get to rename the group they left.
And then turning around and using this vapourous (yet somehow fundametally essential) nothingness to stake out swathes of the meterial world which have been organized around physical, sexed bodies. They readily conflate the two when convenient, and yet, when it suites them, ridicule those opponents who (they claim) can’t tell the difference. Transactivism needs this conflation and equivocation in order to appropriate women’s spaces. If it stays entirely in their heads as a personal, “spiritual” belief, mind game, or hobby (which is where it belongs), everyone else, especially women gets to ignore it and go about their business unbothered and unmolested.
Instead, trans beliefs have spilled into the real world inhabited by everyone. Transgenderism rejects the idea that this is a psychological condition requiring treatment or counselling to combat delusional belief. Instead, it demands that their delusional belief (which, ironically, results in the lifelong, medicalized pursuit of an impossible, material goal), be forced upon society as a whole, again, particularly on women, whose rights and spaces must be dismantled and colonized. Women become the inevitable hostages to the trans political agenda. Far too many people of both sexes(!) are happy to accept this brutally steep price.
In order to gain the “validation” as the “real” women they claim to be (but never shall be), trans identified males have to be able to move into women’s spaces, which have, historically, for ever and always, been segregated by sex, not putative and newly invented “gender identity”. This is why third spaces for trans identifying males will never be accepted. Ghettoization just emphasizes the “transness” which they are so desperate to escape and leave behind, like thier “deadnames.” “TWAW!”
(That the police, courts, and media have played along in such things as hiding the sex of male offenders by using “preferred”, dishonest pronouns that magically turn male crimes into female ones is a scandal in itself, and the desired conflation that tansactivism has always sought. Same with the male invasion of women’s sports, hospital wards, prisons, etc., where the issue is conveniently and obscuringly framed as illegal, bigotted rejection of “transness”, rather than legal, principaled, prudential resistance to invasive maleness. Women are supposed to “be kind”, to shut up and accept this prelude to abuse, molestation, and rape. Media complicity in this is not incidental or accidental. It is a deliberate strategy, requiring care, premeditation, and an enforced editorial policy to maintin the lie. Ditto the efforts of governments, NGOs, and corporations. While porayed as “just” and “compassionate”, trans “rights” as presently constituted and promulgated could never, ever have been either. The only way it succeeded as quickly and thoroughly as it did was because it rode on the background radiation of sexism and misogyny that had never really left these institutions, and society in general. If feminism had won the war it had been fighting, trans “rights” would have failed, because everyone would have seen how dangerous and unjust they were to women. Women raised the alarm, but it was not enough. Trans “rights” were taken up in the face of women’s opposition, in spite of women’s opposition. The clear message behind all of this is “Fuck women.” Literally.)
Women are not allowed to leave; they must be forced to accept male presence in female spaces; exile of trans identified males to third spaces precludes this validation. Validation is the whole point of the operation. Violating women’s boundaries is the whole point of their political program, which is why they had to scream “NO CONFLICT!” loudly enough to drown out the women protesting this very conflict.
Thus trans activism must deny the reality of sex (which barsTiMs, as men, from entering female spaces), while at the same time they depend upon the existence of biological sex, for the female-only spaces they need to access for the “affirmation” of their “womanhood.” Consequently, women cannot have anything free from men. Ever. What greater confirmation of a TiM’s “womanhood” than sex with a lesbian? SCORE! This need to destroy/become the hated/desired “other”, I believe, is one of the core contradictions at the center of gender ideology. Others are the belief that desire, ideation, and “dressing the part” can produce a change in biological sex (TWAW!), and that, indeed, humans can change sex in the first place. Genderist knowing reliance on thought-terminating slogans (“TWAW”, “NO DEBATE!” “NO CONFLICT”) and emotional blackmail is a clear admission on their part that a moment’s thought is all that it takes to reveal these foundational contradictions, and demolish the very basis of their political agenda.