No one asked you to present the notion of Santa Claus as truth. They just asked you to read the damned poem and shut the hell up. They also didn't ask you to tell the kids that it was their parents who bought the presents, denying them of the traditional Christmas fun that so many parents and children enjoy.
I bet you teach the "ozone hole" myth as fact. I bet you similarly teach the darwinist macroevolution myth as fact. I'm sure that your depiction of Martin Luther King is as mythical as most current depictions. Yet you pretend that you won't "teach" that Santa Claus is real when all you were asked to do was read a poem.
If you were my child's substitute teacher, I'd punch you in the mouth for this.
"If you were my child's substitute teacher, I'd punch you in the mouth for this."