Traitorous criminals have been walking around commiting subversive activities since the beginning of time.
This happens in ALL nations.
The only place it can even be CURTAILED is in a complete dictatorship.
Look around.
In the U.S. we all kinds of subversive groups with are freely allowed to plot and plan till we can catch them actually DOING something illegal.
Take your pick: we have communist groups, anarchist groups, fascist groups, white racist groups, black racist groups, latino racist groups.... just take your pick.
So, now that we've established this is a verifiable reality...
it's only a matter of investigating which particular people or groups actually DO this sort of thing.
To say this has never been perpetrated by the government, or members of a government agency, would be untenable.
There are records of the CIA getting hauled in front of Congress, many times, and found to be involved in all kinds of subversive and criminal activity.
It's in the congressional record.
We KNOW these things have happened.
So postulating that it's STILL happening is completely reasonable.
For goodness sake, go look at the latest dump of wikilleaks... which the CIA has essentially confirmed.
We live in a fallen world.
Crap happens.