Arlyn Danielson wrote:
 Museum-L would be pretty boring if we all held the same feelings
and opinions on every subject.

I welcome hearing other professional opinions.  I do, however, find your need to keep repeating that same opinion unnecessary.  Restating for purposes of clarification, as you have also done, is of course fine.

(To clarify my position, I obviously don't mind if listers use Museum-L for
museum related information and work- including looking for a place to stay
or live, but it wasn't clear if this apartment inquiry was just someone
looking for a place and thought they would use museum-L, or if it was a
museum work related move.  I don't want to split hairs, but this still
isn't Apartment-L.)

Why didn't you just ask what the purpose of the move was?  Based on the 
e-mail address of the sender it would be fairly safe to assume it was for museum related work.  But if you needed to be certain, you could have simply asked instead of automatically criticizing the person for the posting.