Let’s take a minute to look at some of these “cites,” shall we?
This is a discussion page for editing the Wiki entry on “cisgender” to include a section on its use as a slur. Note that this section does not appear in the actual entry for “cisgender.” Which means it’s an argument that’s too unsupportable even for Wikipedia.
This is a blog post responding to someone who personally does not like the term “cisgender.” The original complaint makes mostly the same arguments made in this thread. Notably missing from the complaint is any indication that anyone has ever used the term as a deliberate slur. It’s mostly “insulting” because the person writing the complaint has not agreed to be defined by the term.
Another blog, this one asserting that… well, something is a slur, but the author kind of forgets to point out what word he’s talking about. “Cis” is a reasonable assumption, but he doesn’t provide any evidence that it’s a slur, and the usage he’s referring to is completely neutral.
Really? Urban fucking Dictionary? And an entry that’s clearly written by someone with an ax to grind with transexuals in general, no less.
Oh, man, this is so close to an actual cite! Unfortunately, it’s still a failure, because you need to show that the word itself is a slur, not that it can be used to construct sentences that are slurs. Also, the footnote for the term being a “negative slur” goes to another blog post, addressed directly to the guy who wrote your third cite. So, the “blogging circles” where it’s become a negative slur apparently consist of cisgendered people with a chip on their shoulder about the term, and not, as your cite misleadingly implies, among actual transsexuals.
Hey, The Atantic! You finally found something that’s not open source or a blog post! Of course, to get to the bit you quoted, you have to read through nearly the entire article to get to a throw away comment about a poll taken on HuffPo about how cisgendered gays and lesbians react to the term - and even then, the reaction does not appear to have been anything like unanimous. (The link in the article goes to a search result from the HuffPo archives, not to the poll itself, so I don’t know what they actually found.)
Frankly, I didn’t think you could come up with a more pathetic cite than the google search you initially posted. But I should have had more faith. At least the Google cite had an actual instance of a trans person using “cis” in an insulting manner. Although, again, as part of a sentence (“Die, cis scum,” apparently the originator of the term), not as an independent slur in and of itself. Claiming that this is evidence that “cis” is a slur makes about as much sense as saying that “black” is a slur because some guy once said, “Fuck those black people.”