A hypothetical for you. Imagine there has been wrongdoing by people in power in this country, imagine there are witnesses to that crime who wish to report it to the FBI. The wrongdoers, having knowledge of this, proceed to call out the agency under discussion and interecept their communications, all in the name of national security. Smacks of tyrany to me. Lest we forget Richard Nixon.
Watergate actually showed that the exedcutive branch is in danger of wrongdoing from the FBI. There was more wrongdoing at the FBI than the White House and "deep throat"(Asst. director of the FBI) was later convicted of felonies while Nixon never was.
Anyone who can wiretaps and spies. There is supposed to be a giant radio installation in Cuba just for monitoring U.S. communications. And I'd worry more about loony Fidel than the U.S. spies motives.
There aren't any secrets, get used to it.