Santa's probably just stressed. We all get stressed around the holidays. He gets a pass on that out of character rudeness. But something's still amiss here: All during the song, the conductor elf keeps turning around and shooting apprehensive looks at Santa, like he's expecting to feel the sting of a whip at any moment. It's easy to see why: All throughout the performance, Santa grows increasingly moody and unhappy, slumping in his chair and glowering at the singers.
"Yeah, great. Call me when you've learned Freebird."
After they've finished their heartfelt ode, the elves turn to Santa and ask hopefully: "How did you like it?" To which he brusquely responds, "Well, it needs work. I have to go,' then storms out and slams the door. That's like giving your dad a drawing to put up on the fridge, only to have him criticize your sense of perspective and ability to use color to evoke emotion.
But it turns out that was Santa's version of "polite." He doesn't actually think the song needs work, nor does he think it's the thought that counts. No, he actively and passionately hates the damn thing. When he hears the elves singing it again later - like some sort of pixie spiritual to dull the pain as they slave away on his production line - Santa has the following exchange with his wife: