I've scanned the relevant pages so that you can see his argument, but more importantly, see the footnotes where he directs you to further sources regarding the rebuttal of this point. He makes a distinction between others disagreeing with R' Hirsch and claiming that R' Hirsch himself believed his actions were dictated by hora'at sha'ah.
Rabbinic Responses to Modernity- Samson Raphael Hirsch
Here is Dr. Leiman's explanation of the purpose of the book (from his introduction):
- The aim of this essay is to present, if only in outline form, a representative account of gedolei yisrael in the early modern period (i.e., the nineteenth century) who sought to relate Torah teaching to general culture. Our focus will be primarily, if not exclusively, on their differing viewpoints vis-a-vis general culture, on the institutions they engendered, and on their impact on the Jewish community at large. This essay does not purport to be an exercise in either history or biography; nor does it make any claim toward comprehensiveness. Rather, it is an attempt to engage in intellectual prosopography, i.e., to present a portrait of one aspect- albeit a crucial one- of the attitudes of a select group of gedolei yisrael who confronted modernity with an openness to general culture. Any attempt to portray all gedolei yisrael in the modern period who, in one form or another, reacted positively to general culture would have resulted in a lengthy monograph, at the very least. Such a volume would surely have tested the patience of most readers, and - in any event- would have moved well beyond my ability.
No hidden agenda need be sought in the presentation. It is intended to be largely descriptive and, hopefully, accurate. Wherever possible, the positions of the gedolei yisrael will be presented in their own words.
One final word. Feelings run high about some of these figures and their respective positions on Torah and general culture. In the heat of argument, their positions have often been misconstrued and misrepresented. It will be no small accomplishment if their views are set out dispassionately and accurately. To the extent that there is an agenda in this presentation, it is a transparent one: to demonstrate that the positions described in this essay are real, not imaginary. They are legitimate alternatives within Orthodoxy, to be accepted, rejected, but not ignored by those genuinely committed to traditional Jewish teaching.
~"Rabbinic Responses to Modernity" by Dr. Shnayer Z. Leiman, pages 9-10