The only reasonable explanation is the poll is done on a very private or paranoid group
This is false, even if we limit ourselves to only legal danger. If you say something to two people, and one of them repeats your words to the police, the police can easily ask the second person for confirmation. Add a few vague "lying to the police is very serious" threats, and there's a good chance the second person will betray you.
Heresy - questioning the orthodoxy of today's doctrines - carries a high punishment these days.
I wrote in another comment [1] why people might be wary about voicing their opinions, TL;DR: polarizing topics with staunch opinions from both sides (and about the other side) would lead to heated debates.