Ah yeah, the survey asks "Do you think you can say anything you want freely, or do you have to watch what you say on some topics?", and the blogger rides the Stasi and fascism horse about governmental free speech restrictions, although no such thing was discussed in the survey.

The survey question and results itself, page 24 for this 18% figure: https://www.ifd-allensbach.de/fileadmin/user_upload/FAZ_Mai2...

Google translation of the question: "Would you say one can freely express one's opinion on anything in public, or does one have to be careful about some or many topics?"

The German summary linked from his blog says "The rude forms of argument are given as the reason for this low value.".

The survey doesn't even ask how the people lean, and I know during the refugee crisis, even pro-refugee people are wary of discussing that topic, because somebody at the next table in the bar (or sitting opposite you in your own kitchen) could have a different opinion and everybody was very firm in their belief, leading to heated debates. The observation was, "Flüchtlinge" ("refugees") was the new F-word.