> If the warrantless surveillance includes information such as the time and place of where you plan to commit a crime, law enforcement can stop you for a random check on the way there, giving them actual evidence for prosecution.

why is that a bad thing?

If the crime is victimless (such as any drug usage "crime"), then the issue isn't with the police, but with the state defining what "crime" is, and that definition doesn't align with the people's definition.