(1) Santa's coming to my house. Don't get me started -- the fat man cometh, and if you don't like it then don't leave out milk and cookies at your house. And don't leave out a salad for the reindeer either, punk. Just go to bed and be a miserable, dour adult and don't suck the fun out of my family celebration time.
(2) Hey teach: let's assume that Santa is harmful and false for a moment for the sake of argument. Are you going to pipe up at Kwanzaa, too?
(3) Now let's assume that Santa is not harmful and false. For what purpose is it necessary for you to impose your will on these children if their parents are very happy to encourage a celebration which makes these children happy and allows the parents to teach a message of selfless love that can be then applied (as they see fit in their homes and not by you in your classroom) to the actual story of Christmas and the delivery of a gift more precious than Santa can bring? Who asked you?
(4) Ever bounce a check? How about missing a payment date on a bill? Or how about this one: have you ever told a lie to get out of doing something at work? Let's not get all screwball over Santa when I am 100% confident that people who call the jolly fat man a "lie" are themselves capable of and culpable for far worse lies -- bigger lies than Santa can possibly be if Santa is a lie. If you have ever done any of these, lipping off about how you object to teaching children falsehoods is simply self-inflation beyond the scope of your moral reach.
People who dally with Santa as a moral cause for objective truth make my skin itch. What a stupid place to make a moral stand: on the backs of intellectually-defenseless children who are your captive audience. That's some kind of moral heroics, I'll tell you.
And don't start me on so-called "Christians" who don't "do" Santa. Jerks.