I'm surprised that no one is addressing the real answer to this question, which is posted above. AA does require this passenger to book a 2nd adjacent seat. There is nothing wrong with requesting that AA follow their own policies. This passenger should be moved to a seat with a vacant adjacent seat, or, of unavailable, be asked to deplane. Really this is on the GA -- they should not have been allowed to board (IMO it is much better for all involved to handle this situation with private conversation at the gate than a public one on the plane)