Dude we can differentiate between someone lying to us to deceive us or someone 'lying' to us to make us happy/help us. At least in retrospect.

Sure maybe the kid in this post can't trust his dad anymore. But he can 100% trust that his dad always wanted the best for him.

people who try to live 100% deception-free are deceiving themselves

it's more important to teach kids when to be truthful (when they're young, that's almost always) and when to be politely or justly deceptive (when the next door neighbor asks if you liked her cookies you say "yes" even if they sucked, and when a police officer asks if you've seen the kid in this photo you say "nah, I don't know him")

"mom lied about Santa!" eventually gives way to "I'm glad my mom created Christmas magic for me when I was a kid, so that I could enjoy child-like wonder and traditional holiday mythology"

I get what you are saying but at the same time I can relate to your friends as well. It's definitely not a hill I would die on and I wouldn't judge a parent who made a different choice than me, I don't think there is a objectively correct answer here. I also don't think it's a huge deal either way.

I think OP's story would have hit a little different if the Dad had been the one to tell the son about portals to the Ether in the first place.

I'm sure everyone reacts to the information differently and it probably depends on how young you are when you find out, what kind of relationship you have with your parents, and how sensitive you are about honesty.

It wasn't a big deal for you when you learned the truth and I'm glad. I'd be willing to bet your friends had different experiences though. I think they are both valid.

It wasn't a huge deal for me, but I remember how I felt when I found out and it isn't a happy memory. I didn't exactly never trust my mom again, but I did learn that no one in life- no matter how much you trust them- will ever be 100% with you all the time. That's part of growing up and every one has to learn it sooner or later, but it just seemed like it was unnecessary. I was also 5 years old when I figured it out, I'm not sure if this is particularly early or not but I remember it was kind of a bummer.

I'm sure from my moms pov she had fond memories of believing in Santa and wanted the same thing for her kids. I don't' ever remember thinking it was like a malicious thing, but I also couldn't help but notice how it was used to keep my younger brother and sister in line. "If you don't behave Santa won't come this year" type thing, so at least part of it was feeling manipulated.

TLDR: don't judge your friends too harshly. They probably have reasons to feel like they do.