[What follows is based on ongoing conversation with my co-author, Merel Lefevere.--ES]
Institutions (that is, legally or corporately sactioned rules to be followed) can be designed or have been developed for solving particular problems or for particular aims. Yet, in the fullness of time outcomes under these institutions can reveal a pattern of unintended side-consequences. Let's say that one such unintended side-consequence is the fixation of certain (informal) norms or a pattern of exclusion. If some group (the insiders) benefits from this side-consequence they will sooner or later notice it often before the people who do not benefit from these. Human nature being what it is, often the disadvantaged outsiders are the first to speak up about the unintended side-consequence. The outsiders are at a disadvantage when they do so because if the side-consequence is really harmful they are fighting it with relatively slender resources while trying to figure out what the hell is going on. One especially pernicious aspect of the toy-example described here is that all the insiders think they have clean hands. While they actively benefit from an outcome pattern, they can always claim that none of them intended it or actively promoted it. So, when individuals are called out on, say, the informal norms and how these facilitate the pattern of exclusion, the more outspoken of the insider will fall back on variants of what we may call "The-Everybody-Did-It Syndrome" or (TEDI). Many other insiders prefer Hiding In the Herd (HITH) and focus on their work, career, etc.
In the real world we find TEDI annd HITH among bankers defending their bonuses even in the face of tax-funded bailouts as much as among academic philosophers defending a shameful pattern of sexual exclusion. TEDI is indicative of collective negligence and, if noticed, it becomes a collective action problem. Short of abolishing the institutions entirely (i.e., revolution, which is always dangerous for its potentially far worse unintended consequences to all), the best that can be hoped for is a change in the informal norms with which the institutions operate. This can happen when enough of the insiders are convinced that it is in their enlightened self-interest to change systematically how the rules are interpreted/applied or to alter the informal norms. Sometimes change comes from moral clarity, but in practice the insiders decide that it is not worth their energy to keep defending a crappy practice (to their peers, tax-payers, etc). The sad thing is that philosophers are no wiser than bankers in these matters.