Before Snowden, it went something like this:
"we are only spying on terrorists and military targets."
"The postal secret will never be violated. Mail and emails by extension are safe forms of communication."
"A warrant is needed to listen in on a telephone call. Telephone call is a safe form of communication."
"Building a database on the citizens political affiliation is illegal, and ground for political dismissal of officials."
"The ISP, email provider and telephone company is only a common carrier. They are not allowed to watch."
"Warrants and subpenas are directed at individual. Collective punishment is wrong, illegal, and something only other countries do."
"The government job is to protect people. If the government know of a serious vulnerability in society, they will inform people in order to protect them."
"Only criminals breaks into computer systems."
knowing that the US government could lie on all those points is not the same as knowing that they are. Tinfoil hat was define as such because they thought the government lied on those points, based on the fact that the government could do it.