Free Software preserves our system
When thinking about Free Software, it should be seen as an encompassing concept for a reliable, sustainable and dependable information and knowledge society involving all stakeholders.
The price we are paying for the predominance of the proprietary software approach is high. Because the proprietary software paradigm has a strong, system-inherent monopolising tendency  and software permeates all areas of economy, northern economies suffer and southern countries are given the choice between exclusion or co-suffering in total dependence. That is why breaking up Microsoft without a change in paradigm would not improve the situation significantly. Free Software, on the other hand, brings back competition while allowing cooperation among companies, people, and governments. All of these equally available and empowering to all the peoples.
While minorities remain at the mercy of large multinational companies regarding support for their culture and language when using proprietary software, Free Software gives them freedom to modify all software according to their needs. Thus, Free Software also allows building a sustainable local hard- and software industry independent from monopolies and large multinationals. Of course cooperation with large companies is possible and may be useful, but while dependency is the price to pay for such cooperation in proprietary software, Free Software provides independence.
The design, development and use of software is increasing in all societies. Increasingly, access to software is largely determining our capabilities for education, communication, work and even social networking. This includes building social movements, promoting citizenship and transparent democracy as well as general governmental and health services.
Software in general has grown into northern societies to a very large extent and if development policies are successful, this will also be true for southern societies at some point in time. Therefore software must be considered a cultural technique, sometimes even a cultural good.
For all central cultural techniques, we have to ask who should be put in control of it. Proprietary software puts large northern multinationals in control.  Free Software makes this cultural technique equally available to all the peoples.
For those who are connected - and we surely hope this will mean all the peoples at some point - human rights of participation in culture, freedom of speech and opinion are influenced to a large extent by their control over the software they use, as are freedom of association and movement. Software forms the medium. Unlike the proprietary approach, Free Software gives each person full control about their personal information space. Although this alone is not sufficient to grant privacy and security, it is a necessary prerequisite.
Preventing Technocracy - upholding democracy
Legislation should be developed by democratically elected representatives in a transparent way. Even in situations where this is true, rights that cannot be exercised remain empty. Granting rights on paper does not mean people will have the means of exercising them.
The complexity of modern systems alone makes it a difficult task to uphold democracy in the digital domain, but the overall intransparency of proprietary software makes it impossible. Unless you are using Free Software, the rights you can or cannot exercise are determined by the proprietary software vendor - it is the vendors decision alone, a decision that nowadays is often given precendence over the democratic legislative process.
Good examples are the European Copyright Directive (EUCD) and Digital Millennium Copyright Act (DMCA), both implementations of the "The World Intellectual Property Organization (WIPO) Copyright Treaty" (December 1996). While the DMCA already gained notoriety for enabling censorship of Scientology-critical sites in the United States,  the German implementation of the EUCD is silently making the right to fair use inaccessible. Although laws clearly state that customers have the right to copy a CD for their car stereo or even a friend, those who exercise this right on so-called "copy protected" CDs or on any DVD now risk punishment. And if you think this is where it ends, feel free to read the EFF paper on so-called "Trusted Computing" (TC). 
Proprietary software effectively puts an area that was previously governed by democratically elected representatives into the hand of corporations, therefore establishing technocracy. 
All of our hard work to defend and promote human rights, gender equality, rights of the disadvantaged, a free media, privacy and security, digital solidarity and other issues is in danger of having been for naught if the information age is based on proprietary software.
Free Software alone is certainly not enough to overcome all problems - but it is a necessity to empower people to exercise the rights we are fighting for in the information societies.
 Explanation of these mechanisms will gladly be provided, if of interest.
 Side note: Which should not be understood as a good thing for people in the northern countries. It is not.
 For reference, see
http://www-camlaw.rutgers.edu/publications/law-religion/scientology.htm (not available any more)
 Technocracy: "Government by technicians or management of society by technical experts." (Merriam Webster Dictionary)