My brother’s faith was greatly affected when he found out Santa wasn’t true. He is big on truth, even to this day, and it caused a rift in believing my parents about God/Jesus. He did not come back to his faith until he turned 42! So this can be detrimental teaching.
A few quick observations:
i) Anyone whose faith is that flimsy ought to have the props kicked out from under his rickety faith. He needs to lose that kind of faith to make room for solid faith. He needs to lose faith in his parents to find faith in Jesus.
It’s fine to be that trusting when you’re four-years-old, but you need to wean yourself from emotional dependence on mom and dad. They’re only human.
Overreactions like this simply illustrate the fact that some men and women have great difficulty growing up. Psychologically, they are frozen in childhood.
I don’t say this to justify the Santa Claus custom. Whether or not that’s permissible requires a separate argument.
ii) Skimming through the meta, which went on for 210 comments, I was not surprised to notice that it was generally women who feared the damage that losing faith in Santa might cause while it was generally the men who brushed that off.
This goes to a basic, stereotypical difference between men and women, fathers and mothers. As a rule, mothers instinctively protect their kids from risky, rough-n-tumble behavior whereas fathers instinctively encourage their kids (especially their sons) to be adventurous and take risks. These are both needed. They counterbalance the extremes of one to the exclusion of another.
iii) The Santa tradition isn’t intrinsically important. It only becomes important when some people make it more important than it really is. I have a take-it-or-leave-it attitude towards the Santa custom. But some opponents act as if this is hugely consequential.