Liberationism and bathhouse culture were closely intertwined, and bathhouse culture had been a bête noire of the assimilationist faction for some time before AIDS showed up. Demands to "stop having sex", or at least to stop having sex in this particular style, were a longstanding feature of that internal conflict, and it wasn't unreasonable early on for folks on the liberationist side to regard this newest call as essentially just more of the same. As the scope and gravity of the problem became obvious, people did gradually change their behavior, but the relatively long asymptomatic period and relatively high transmissibility of the virus meant that, by the time that happened, it was too late to do all that much good.
Sure, an early and assertive response within the community might have had a real effect on the outcome. But this is well within the territory of expecting people to act on the basis of perfect information which, at the time for action, neither they nor anyone else actually had - or, put more succinctly, of presentism in the historiographical sense. I don't blame Shilts for that; he wrote in 1987, when the crisis was still in a very real sense ongoing. We, by contrast, have the benefit of a quarter century's distance and study from which to look back on those days now. We can do better, and should.