And privacy is a prerequisite for free speech :

“If a man's privacy can be invaded at will, who can say he is free? If his every word is taken down and evaluated, or if he is afraid every word may be, who can say he enjoys freedom of speech? If his every association is known and recorded, if the conversations with his associates are purloined, who can say he enjoys freedom of association? When such conditions obtain, our citizens will be afraid to utter any but the safest and most orthodox thoughts; afraid to associate with any but the most acceptable people. Freedom as the Constitution envisages it will have vanished.”
- Justice Douglas

“Among deprivations of rights, none is so effective in cowing a population, crushing the spirit of the individual and putting terror in every heart. Uncontrolled search and seizure is one of the first and most effective weapons in the arsenal of every arbitrary government. And one need only briefly to have dwelt and worked among a people possessed of many admirable qualities but deprived of these rights to know that the human personality deteriorates and dignity and self-reliance disappear where homes, persons and possessions are subject at any hour to unheralded search and seizure by the police.”
- Justice Robert Jackson