Your post seems to be based on the premise that there is a government-level conspiracy.
Anyway, if they did I would pay massive attention, then I would get worried: no good can come from first-contact, we're still a very primitive civilization compared to what we could be, and we don't need external influences that would just mess things up.
And then there are theological issues to contend with.
Why are you asking this all of a sudden?
Not to worry, I hear that the aliens have a book titled To Serve Man. What could possibly go wrong?