Not all censorship is equal, nor does all arise from government or external force.

Not all censorship is equal, nor does all arise from government or external force. People self-censor all the time; such restraint can be part of the price of rational dialogue. The artist Ben Shahn's poster illustration reads: "You have not converted a man because you have silenced him." Silence can indicate a forced assent, or conversely, it can be contemplative, a necessary part of dialogue that rises above the din of quotidian life.
excerpted from http://gilc.org/speech/osistudy/censorship/
http://gilc.org/speech/osistudy/censorship/