Of course you need to be able to hide your political speech; people automatically temper their opinions to conform more with the group or choose to remain silent in situations where everyone's political speech is visible. Without the ability to keep cloistered political speech as a realm to discuss and test ideas without condemnation, the political speech landscape begins to look horrifically uniform and (inevitably, because they control the media) pro-state. To reiterate, if the state has the ability to spy and understand 100% of online political speech, people will self-censor their speech, preventing different ideas from propagating.

This is currently the case-- radical political ideas have been accompanied by state surveillance and attempts at discrediting for a long time, and the current crop of NSA totalitarianism is no different.