... However ...
If you refuse to answer direct questions posed by a Census employee, or interfere with their ability to collect data they can make a civil or criminal referral to DOJ, depending on which is appropriate.
I got that darn thing like 5 years in a row. I had moved 4 times in those years. I tossed it and when they came to the door I said go away. They went to the next farm down the road to pester them about me and who lived there and where told to eff off there as well.
Nothing happened to me.
I highly doubt anything would happen to anyone if they told them to bug off.