The role of the LGBT community is three fold in that it provides support, oversight, and advocacy. Without the LGBT community the rights of gay and transgender people would be decades behind where they are now and numerous people would still be living closeted lives that were filled with fear. While it is true that for far too many that is still a sad reality, it is far less than it had been even 15-20 years ago which is a major step forward. While the contributions of individual members of the LGBT community have been enjoyed by nearly everyone on earth knowingly or not, it is the larger organizations that in large make those contributions visible and in some cases possible.
The sad reality is that many LGBT persons find them self lacking support from friends, families, employers, and even spiritual organizations when they come out. As ridiculous as it seems you can go to any major city and find teens that have either run away or in some cases been kicked out of their home because they had nowhere to turn when they came out. Organizations like PFLAG help fill that void by providing support and education to the friends and families of these people so that they have the best odds possible of maintaining those bonds and not being stigmatized just because they are not attracted to members of the opposite sex.
Because of the tremendous efforts of such organizations the attitudes of future generations are changing far faster and easier than in the past. The rise of GSA's (Gay Straight Alliances) in schools or localities where schools won't allow them has been a tremendous tool in this regard. GSA's serve as peer educational/support systems which are a tremendous aide for gay teens that either lack or get less support than they need at home, and they are great for their straight members as well as they get the opportunity to learn the truths about homosexuality rather than the myths so that there is less of a barrier between the two.
The second faction of the LGBT community is the oversight which is carried out by numerous watchdog agencies like local and state Pride Organizations all the way up to larger national organizations like the Human Rights Campaign (HRC), and even international organizations that dedicate at least a small portion of their focus to the gay community like Amnesty International which has long reported the inequitable treatment of LGBT persons everywhere they occur. Without these organizations there would be no flow of communication nor concerted efforts to avoid the waste of resources. What agencies like this provide is primarily information on everything LGBT related, whether it be what locales are and are not gay friendly, which employers/businesses have a history of discrimination, and what politicians say they will support the LGBT community and whether they really do or not.
By working in concert they each provide bits of information in regards to each of the above types of issues and then verify them so that the public as a whole has solid accurate information. Prior to these organizations LGBT persons often had little idea as to most of these things other than word of mouth or through the media, both of which were often inaccurate to start or became inaccurate in the re-telling. With this organized oversight and dissemination of information, the LGBT community not only had the knowledge needed to make changes, but the clout of a global community to make those changes happen quickly. Companies that refused to treat LGBT persons equally found them self losing business and potential employees on a widespread basis, and politicians that did the like lost endorsements and campaign contributions.
Finally the enforcement segment of the community is seen in organizations like Lambda Legal, GLAAD, and SLDN which carry out many of the legal battles. Whether it be serving as legal counsel in the fight for gay marriage or aiding the victim of a hate crime or unjust workplace termination, for the gay community as a whole these are the pit bulls. They stay on top of every issue and insure appeals are filed when necessary, laws are being followed, and that when they are not that consequences for transgressions result. While these numerous organizations often go unnoticed aside from GLAAD, they are of paramount importance as they are the teeth of the gay rights movement and defenders of the community as a whole and for individuals.
It is through the efforts of such organizations that people are feeling less afraid to come out of the closet and carrying less fear that the decision to be open about their sexuality doesn't necessarily mean losing everything they worked to achieve. The gay community is finally reaching a point in which its members feel safe enough to be them self and make make more positive contributions to the world as whole which benefit everyone, not just LGBT persons.