Term for an inability to accept ideas that are outside the norm
At an individual level, a person that refuses to even consider an idea that goes against his or her existing beliefs would be called close-minded or narrow-minded. 

Intolerant and prejudiced can also be used, but intolerant tends to be applied when discussing religious or political ideas, and prejudiced when talking about racial relations. 

Conformist can also be used, and is a more neutral term. It's also a bit vague, so you'd have to specify which idea or range is being conformed to.

A public discourse limited to an acceptable range of subjects would limited to "safe topics". 

A person who can accept or generate ideas outside of socially acceptable opinions can be labelled a free-thinker. Depending on how far outside the norms the ideas are, the person and may be branded a "radical" or even "pervert" in order to indicate society or government's disapproval of the individual.