Why does the ACLU try to change the real meaning of "separation of church and state"?

What's the point of arguing this when the average user of this site thinks The Federalist Papers are what Obama puts down for his puppy? Most people don't even realize that the term "wall of separation" was coined by Baptist minister Roger Williams 150 years before Jefferson appropriated it in his letter to the Danbury Baptist Association, which letter goes almost unread today.