Start with the South China Morning Post, the main English language newspaper here which has been covering this story extensively. The current editor, Wang Xiangwei, joined in 2011, is a member of the Chinese People's Political Consultative Congress, and has been criticized for self-censorship multiple times since taking over.
Then you have the political system here, where people can vote in local elections but not in the main election that actually decides the Chief Executive (President). The current CE, CY Leung, was dogged by accusations that he was a Communist Party member throughout the election period. These accusations were not without merit given his political history (appointed to a prominent committee at a young age, a position traditionally occupied by party members), and these issues have not died down since he's taken office.
It makes no sense for Snowden to have come to HK for its political freedom. Neither is this city a hotbed for political dissent. The Occupy movement here was largely ineffective (there were often more homeless people than protestors at the camp), and power here is concentrated in the elite (HK has one of the highest Gini coefficients in the world).
He came here because here he can leverage China vs the US. Any talk of political freedom or appreciating the culture is pure fluff.