If I were able to do much in-store shopping this year, I would have loaded up the cart, gone to the counter and wished the clerk a cheery MERRY CHRISTMAS!
In any store that forbid its clerks from answering in kind, I would give the stink eye, note that I was Christmas shopping, that I intended to buy Christmas presents, point out the logical disconnect in buying Christmas presents from a store that doesn't celebrate Christmas, turn on my heel and walk away.
Any store that doesn't get the message after having to restock multiple abandoned carts probably doesn't deserve to be in business...