Earlier quoted context omitted.
Because a government has _never_ done anything illegal before(!)
After the Church Committee, it is very difficult for the government to do illegal things and for it to remain a secret. That's why in all of Snowden's leaks, he revealed only a single extant illegal program, and its legality wasn't so clear that it couldn't be argued in court. Beyond that, you ignored my previous argument. If they were already doing this, why bother to collect metadata from taps?
These programs all overtly violate, amongst other things, the 4th amendment, but the structure of our legal system makes it effectively impossible to legally challenge them.