I do not know wher eyou got that number from, but my impression is just the opposite. Most people I encountered either do not know what unions would do for them or have a negative image of unions (ranging from "they used be good but not anymore" to "they are a corrupt bunch interested only in my money"). There are two factors responsible for such attitudes: (1) employer propaganda and union-busting and (2) low employee identification with the workplace. Most people in the so-called secondary labor market (shitty jobs with little security and promotion opportunity) either view their work as a temporary arrangement and thus have little incentive to make an effort to change it (you would not invest in renovating a rented appartment, would you?) or work in small establishments wher epersonal relationship can be more effective than union membership (e.g. restaurants). Those working in t6h epronary labor market are either already unionized (cf. auto-workers) or work professional jobs that either prevented form unionization or offer little gains from unionization.
What is killing unionization in this country is not AFL-CIO but the legal prohibitions of industry-wide unionization (as in Europe). Industry-wide unionization does not require costly factory-based unionization drives, and offers benefits to all employees in an industry, even those working in small establishments. Moreove, it offers less incnetive to oppose unionization by individual employers because it creates similar "disadvantage" to all competitors, as oppesed to selective "disadvantage" to those who allow unionization.
Let's just face it: the United States of America sucks big time. It is the institutional complex that is extremely inhospitable to any form of progressive activism: from labor organizing, to peace movement, and to environmental protection. Until this institutional complex is destroyed or seriously weakened, any chances of progress in these areas are very small, indeed. It thus makes littke sense to blame the organizers for the lack of success.
Wojtek