Making a mountain out of a molehill is par for Sir Alex.
Then channeling Allardyce to air his grudges is even better. He knows Big Sam and Rafa have a history. Its a bit like this. Rafa's description of Everton being a 'small club' is to challenge them to win against Man U. The media then picks up on the meme of a stumbling club and the players internalize it. SAF is a bit worried about his club's psyche at this delicate juncture.