I genuinely believed, back in the days when he was all over the talk show circuit debating such luminaries as George Galloway, that Pink News's Benjamin Butterworth was a transman. (And I thought he looked great; just in terms of physical appearance it seemed to be a much more successful transition than when he had transitioned from white to black.) I thought, because Butterworth was constantly talking over trans people and explaining how being trans did not work the way actual practitioners described it, that he likely had transitioned a long time ago (explaining his identifying and promoting himself as a far superior subject matter expert than others who had perhaps transitioned more recently). However, he turned out to be a perfectly ordinary run of the mill 20th century-style non-trans man.
I think that the appearance of very similar non-self-aware and overprivileged hubris combined with ignorance is what is aggravating people in this case. Michelle doesn't just say "I'm not trans" as a statement of fact, which I don't think anyone would oppose. She goes to great lengths to justify and prove that she's not trans but she does so in ways that are, frankly, transphobic and show that she has no clue about the subject. Her comment that she can't be a trans woman because she has a cervix has been thoroughly debunked by the UK Foreign Secretary, just for example. And she clearly spends no time on Reddit - one of the only places on the internet where trans people have both reach and power beyond their tiny demographic - if she thinks that transwomen can't have a vagina and can't menstruate.
And at the same time, she's hypocritically insisting that everyone else is transphobic. And she's insisting that people who have a long history of feminist activism are not feminist, but simply opportunists who care only about hurting individual trans people, and that she herself is an exemplary feminist - even though the logic behind that claim is inherently misogynist. And she's calling random strangers bullies when she herself is visibly bullying, both before and after the "are you trans" question came up. It's classic DARVO.
Comparisons are never exact but: let's say you've been shouting out of the blue, perhaps in progressive empathy with the Scottish Independence movement and the universal human right of self-determination of peoples, that SCOTTISH PEOPLE AREN'T BRITISH!!! And in response, someone assumes that you must be Scottish or you wouldn't be speaking for Scots, most of whom know that we ARE technically British but also realise that it can be a complicated cultural question in some contexts. And most of whom would not like to lose what may be their only existing citizenship unless and until there's a viable alternative.
You then take enormous offense and start ranting and raving that you personally CAN'T be Scottish and everybody else are racist anglophobic xenophobic right-wing bullies who care nothing about anything despite their actual real world records of activism and are totally stupid and craven and beneath contempt for suggesting/assuming that you're Scottish. You then cite as evidence of your non-Scottish status the fact that you have a UK passport, like fish and chips and the King, drive a Jaguar, and can post a picture of yourself in London when you were seven.
The people you're railing against are, reasonably I think, liable to be annoyed. And yes, if you've DARVO'd this group of people on an ongoing basis for eons, some of them are likely to seize the opportunity to demonstrate that you are being unreasonable. Which won't do any good if you're an undiluted idiot. (No shade, Michelle: I also prefer my idiots full strength).