Why the crusade? Haym explains his motives through a personal anecdote in his rejoinder on his web site:
When Becoming the People of the Talmud appeared and then won the Jewish Book Council Award for Scholarship, the danger posed by this was clear; nevertheless, I was conflicted about putting my assessment into print. I discussed the matter with one of my oldest colleagues over dinner. He listened carefully and said, “Haym, the only way you can justify the review that you are thinking of is if you state openly what the real reason for it is, the larger issue that is at stake here. You can only do that is by becoming first, a whistle-blower and then stating matters with an explicitness that breaches the proprieties of academic engagement. You have to point out not simply mistakes but also their elementary nature and what they say about the writer’s basic competence.” I thought about this during the meal and, as it was drawing to a close, replied: “Those rules of propriety, and they are good ones, apply when they are superimposed on the quality controls that function as a matter of course in academia. Everyone then understands what is being said by indirection. However, when that community is wholly in the dark as to what is transpiring, those rules must be breached. Look at what happened in Talmud. A few reviews were, in fact, written in the 1960s and ‘70s pointing out the errors of the author and hinting at his ignorance. The criticisms were shrugged off, because people thought, ‘Oh well, everyone makes mistakes.’ They didn’t know that the errors were ones that a schoolboy would never have made. This couldn’t be stated openly because it was against the rules of the game. Look at the situation now. If these rules aren’t finally broken and the whistle blown, there will be little left in a decade.”We cannot help but observe that none of the scholarship in the field that Haym calls "Rabbinics" is scientific, or for that matter even vaguely social scientific. So "facts" are not at issue in judging the worth of contributions to the field. Assertions by these scholars are "opinion and conjecture" about matters that are far distant from us in time, space, culture and language.
Haym has stepped up heroically to claim supremacy of his opinion over Fishman's based on his assertion that by his "rigorous standards of quality," Fishman is illiterate in rabbinics. Therefore her work is worthless. And unless Haym roots Fishman out of the profession, the field of "rabbinics" will be ruined.
So Haym imagines himself to be a scholar-hero. All we can say is, Bravo to brave Haym the Hero.