I mean, it's not really that surprising, the DHS is an organization that openly calls for Americans to snitch on each other, it's even a registered trademark: "If You See Something, Say Something®" [0]

Also not only reserved to the DHS. There have also been examples of people being under surveillance by the FBI, and ultimately going to jail, over Facebook posts [1]

[0] https://www.dhs.gov/see-something-say-something

[1] https://www.theguardian.com/world/2018/may/11/rakem-balogun-...