The book is about the first few years of the AIDS epidemic, and chronicles the arrogance, denial, indifference and general dickery that delayed anything resembling scientific progress almost until the '90s. This section comes after it's revealed that one of the main personnel at the CDC, who had been systematically denying funding to AIDS studies, had a bunch of posters of shirtless male soccer players in his office:
It was a truism to people active in the gay movement that the greatest impediments to homosexuals' progress often were not heterosexual bigots but closeted homosexuals.
Among the nations's decision makers, the homophobes largely had been silenced by the prevailing morality that viewed expressions of overty hostility toward gays as unfashionable. In fact, when not burdened by private sexual insecurities, many heterosexuals could be enlisted to support gays on the basis of personal integrity. By definition, the homosexual in the closet had surrendered his integrity. This makes closeted homosexual people very useful to the establishment. [...] The closeted homosexual is far less likely to demand fair or just treatment for his kind, because to do so would call attention to himself.
In other words, next time someone taps their foot in the bathroom stall next to yours, stomp on it.