J. Chris Miller
I believe I read in another post that enemies that are placed in a space from outside the board do not immediately fight you, even if they have the "aggressive" symbol.
Enemies will only fight you when they move into your space (or you move into their space).
EDIT: Fallout Rules Reference Page 6 - Enemy Abilities:
"An enemy with this ability being placed or becoming active in the same space as a survivor does not cause a fight."