http://www.popehat.com/2013/09/10/speech-and-consequences/ describes it well:
> Speech is designed to invoke private and social consequences, whether the speech is "venti mocha no whip, please," or "I love you," or "fuck off." The private and social consequences of your speech — whether they come from a barista, or your spouse, or people online, or people at whom you shout on the street — represent the free speech and freedom of association of others.
> Yet people often confuse these categories.
I believe you are making the same confusion between the right of free speech - Eich can support a political position - and the freedom of association so employees of Mozilla and OKCupid need not be associated with a company that has Eich at its head. (In the employees' case, the right to quit.)
There can be and is a tension there. As a country we have said that the right of free association is limited while at work, and that certain factors - race, religion, country of origin, etc. - cannot be used to discriminate between employees. But other factors, like disrupting the office every hour on the hour for a boisterous rendition of the National Anthem, can be grounds for punitive action.