Nowadays we use our computers to do all manner of communication. Both public and private. These can be in the form of text, images, audio and video and in a more abstract fashion - computer programs. As such computers have become a corner stone of modern society with almost all communications being transmitted via these systems.
This is a cause for concern when it comes to free speech. If a program is non-free, then it is possible to have not only others see what you are doing but also limit what you can even use the software for.
This has two major issues.
Firstly, privacy can be invaded and have their own private creations be read and used against them even if there was no intention for public release. Secondly, by limiting what people can say in public - there is the real risk of free speech being restricted. This applies both on a governmental level and a private level.
This has the potential to limit society as a whole. Without active decent and a questioning community then it is possible to have peoples voices silenced. This can be used to limit people challenging a current power, can prevent a new power from rising and completely destroy the idea of an active democracy.
With non-free computer programs there is also the risk to whistle-blowers. Those people that wish to expose a secrete that the public should know. Without a grantee how a communication and a program works, there is a real risk of others listening in on communications. The mere act of having people question if they are being watched is known as 'social cooling'. It can prevent people from raising their voices anonymously for fear that they are being watched already. This can have disastrous results on a civilization as it prevents major issues from being aired for all to see and discuss.
The programs that can impact free speech can come in a few forms.
Those that main use is communication. If the program is non-free then the communication cannot be guaranteed to be private. Without the source code for others to inspect and verify how a communication is encrypted and transmitted, then there is no way that we can verify if it is not talking to someone else at the same time. This is a big issue for journalists and whistle blowers who do not want to be identified.
Programs that looks to be doing one thing but in the background do another. This can be any program that you use to create or collect information. This can be a text editor, image editor or even just the book marks and browsing history on your web browser. These can look harmless when in use but they could also be transmitting information or whole copies of all the data to someone else's computer.
Programs that have entirely different appearance to what if happening in the background. These can be programs that say they do one thing but are actually malicious in the background. A good example is on non-free mobile phone app stores where a program may have a simple function but is actually using that function to get to your information to be sent to someone else's computer. Such programs have been found where they appear to be a game or flash light application but are actually taking all your contact information.
Any of this information is not only a breach of privacy but will only encourage people to not create content that could potentially be used against them for fear it will be used against them.
Free software however is software that tries to avoid these issues by being as transparent as possible. By having source code that programmers can study and modify to fix potential issues then programs that work for you can be produced and not ones that try to oppress the users. Communication systems can be produced that allow for private communications between individuals and groups without the fear of "big brother" watching.
With out computer systems that respect these freedoms and the rights of privacy for the greater good of society, then it weakens democracy as a whole. If you feel the need for this privacy then you should demand systems that run 100% on free software. It is the best defense that you have against malicious interference by others.