You simultaneously complain that you’re being called an elitist gatekeeper and in the same damn breath call everyone else who doesn’t share your opinions of Arch-purism stupid. That is a textbook example of gatekeeping dude.

The reason Arch users all end up like this is that we’ve all tried to help someone, been run around for hours, and then finally figured out that the problem is caused by some stupid thing that Manjaro did

This is a made up situation. I am an Arch user and I have never been so incensed about derivative differences that I felt the need to restrict help to only pure Arch users like I am running some product support hotline. Please, give me a break. Why do we have to be so damned picky about who we help? There’s always going to be differences between my system and another person’s system which can make debugging confusing, even between two separate pure-Arch systems, but that’s part of the fun! And so what if they’re using Manjaro? A ton of problems in the Linux space are distro-agnostic and more due to wrong configuration, etc. If you don’t want to help them, that’s fine, just move on instead of pretending like their entire community committed some cardinal sin against you. Can RHEL users not help out Fedora users? What about Ubuntu vs Mint? Is it really so damned hard to be like “Hey, I can’t figure out your problem. It could be that there’s some differences between Arch and Manjaro” and just move on with your life?

It’s fine if you don’t want to contribute to these kinds of things, but insisting Arch-derivative users stop using them and or be shunned from interaction is gatekeeping to be perfectly frank. There are many reasons why some people might prefer an Arch-derivative. Just because you can’t see them doesn’t make them any less valid for other people who have different usecases and preferences than you.