Leaving aside the question of whether someone named “Abbott” could ever be called “Ultra-Orthodox,” Katz’s arguments do bring up some interesting questions.
Katz seems to have two problems with the prefix “Ultra”:
(1) That it is fundamentally derogatory. (“Orthodox Jews seem to be seen as marking the spiritual baseline, while the ‘ultras’ are typed as a kind of fanatic insurgency, sparse but dangerous.”)
(2) That it’s historically inaccurate. Katz points to those who cite Moses Sofer as the originator of “Ultra-Orthodoxy,” and suggest that it’s disingenuous to claim that Sofer deviated significantly from his rabbinic predecessors.
Katz’s first claim may be overstated, but it did make me realize that while most members of a denomination would refer to themselves as “Reform” or “Conservative” or “Orthodox,” most people we call “Ultra-Orthodox” probably wouldn’t self-identify with this term.
The fact that it is, indeed, a term coined by outsiders should give us pause when using it, though my biggest problem with Katz’s article is that he doesn’t offer an alternative. (I think “Haredi” is probably the term most used by those inside the community.)
As for Katz’s second contention, while it is certainly reductionist to claim that a single person (Sofer in this case) created “Ultra-Orthodoxy,” many (if not most) contemporary historians (one example, here) do see Orthodoxy as a 19th-century phenomenon.
While the Jews of the Middle Ages may have looked more like 19th-century Orthodox Jews than Reform Jews, the emergence of the term “Orthodox” (and “Ultra-Orthodox”) did reflect real changes in ideology, communal structure, and religious practice.