Santa Claus is a folk tale version of a Christian who lived about 1500 years ago. I suppose you could argue that letting children “believe in Santa Claus” violates the first commandment. Not sure about the second.
Many Conservative Christians do believe Santa Claus is an attempt by the "atheist establishment" to remove the Christian identity from the holiday, but that's due to a modern interpretation of Santa Claus as a capitalist icon, and the defensive nature of Christian conservatism. No Christian would likely have questioned the "Christianness" of Santa Claus a century ago, when the status of religion in Western society was unquestioned.
I also don’t remember belief in Santa to be common among my friends. I remember one friend who expressed belief in Santa as a supernatural being, and everyone poked fun at him for it.
More concerning is their failure to square the existence of Santa with the 2nd amendment.
Humans are perfectly capable of holding two mutually incompatible ideas in our heads at the same time. That's how we would determine the winner of a contest between Batman and Ozymandias, or between Godzilla and Voltron, or between James Bond and Jack Ryan, or between Hit Girl and Nikita.
The most psychically significant incarnation of Santa is from the Childlike Wonder Mythosphere, and Jesus is from the Abrahamic Monotheist's Age of Legends. In order for them to even meet, they would have to pierce the boundary between worlds, and perhaps exist together in some mutually neutral dimension. But when they cross over, they have to adopt forms and behaviors compatible with that dimension, which is why they look like paper cutouts in South Park and have no bendable knees in LEGO Universe.
Basically put God == Jesus
Is there a man page for this stuff?
The Athanasian Creed and the Definition of Chalcedon are probably the most relevant, as they deal specifically with Christological questions. The Apostles' and Nicene are valuable, but are too early to have the specifics nailed down just yet. (In historical terms, an Arian or Sabellian would be able to agree with their content without too much equivocation or mental reservation.)
The Trinity as a concept is basically just annotated with "you are not expected to understand this," possibly because it attempts to describe a state of divine being which is beyond human comprehension, but more likely because it's actually nonsense.
but the former is more like INFO while the latter is more like `man builtins` (that is, it assumes you already know a lot about the system)