Because this is an official response from the bureaucrats at the Census Bureau, perhaps we should take them at their word. That is, under certain circumstances, government agents can come and kill citizens who do not answer properly.
Personal information is private property.
For example, the rights of association and privacy, the right to be presumed innocent, and the right to be judged by a standard of proof beyond a reasonable doubt in a criminal trial, as well as the right to travel, appear nowhere in the Constitution or Bill of Rights. Yet these important but unarticulated rights have nonetheless been found to share constitutional protection in common with explicit guarantees. I do see many problems with this whole scenario, especially from a government that doesn't trust me to do my own thinking. Thank you for your message regarding participation in the American Community Survey. We are sorry that you feel this survey asks intrusive personal questions.