I don't think in this case "ultra" is being used as a "denigration". I think its being used as a label for a certain mindset within the GC movement that he is trying to explore.
And I think his point is less about "is it reasonable to use pronouns" and more about trying to tease out elements of that mindset.
A working assumption of this essay has been that those of us who are gender-critical value a liberal, pluralistic society, and are happy for people to believe, live, and present how they want as long as they don’t harm others or expect the rest of us to join in. It must be noted that some who reject transgender ideology and who consider themselves to be stalwart gender-critical types very explicitly reject this. Some members of this group refer to themselves as “Ultras” but some get very angry if you refer to them as “Ultras.”
So he's talking about people who explicitly don't think men should be allowed to present in a stereotypically female way under any circumstances and goes further to say that its about "excoriation" rather than "objection".
I can see exactly what he's getting at, it's a discussion I've had many times on here too.
He then goes on to explore why he personally finds the "ultra"/"illiberal" position inconsistent (and I'll cut him some slack for the terms because it isn't immediately obvious how to refer to that subsection of beliefs in GC)
In a nutshell he's saying he thinks if women can wear chicken fillets/padded bras to work if they like, why can't men? And if one believes in sex based equality, logically there is no reason men can't.
it would be difficult in any case to formulate a limiting principle that would identify in a tidy way that would satisfy everyone what presentations are acceptable and what presentations are not acceptable. That is, the line between an acceptable gender nonconforming presentation and what some regard as an unacceptable instance of “womanface” may be very difficult to draw
Agree with him on this.
The motivations of why people choose to present as the do is not really what he's considering, and I would guess (based on how he's explained it) he would think that bit is less relevant because it's personal to the individual involved and wrapped up in the "believe, live, and present how they want as long as they don’t harm others or expect the rest of us to join in".
For me that line is really important because that's where the crossing point is into authoritarianism. If society decided to ban men from presenting as women at work (as an extreme example) that would set a precedent that "believe, live, and present how they want as long as they don’t harm others or expect the rest of us to join in" doesn't always apply and could open the door to other authoritarian action passing off as for the greater good, such as imposition of state religious beliefs, or restrictions on the actions and freedoms of women.
If one thinks that "believe, live, and present how they want as long as they don’t harm others or expect the rest of us to join in" is a fundamental human right (I do) then one has to tolerate others behaving in ways that one doesn't personally like.
I know there is an argument to be made about "performing fetish" but for me that one doesn't hold much water because I think plenty of men are inappropriately fantasising about women all day and so it's not something we can ban or police. Just an aspect of male behaviour (NAMALT) that women have to navigate in a patriarchal world. Preventing trans identified males from being referred to as women will have little to no impact on the bigger issue.