a) GPL software, with the source code readily available and
b) Easy to disable - a single switch in settings
c) Easy to remove altogether...
Rather, most "Linux supremacists" or however you call them I've seen tend to be Arch users, and vigorously promote Arch. Many of them have never tried a flavor of BSD or any other UNIX (such as Plan 9) either and barely even mention it.
Disclaimer: I'm a Slackware user. Although I don't like Ubuntu, it's good to see institutions making the shift. Besides, they need an easy-to-use desktop distribution, they're obviously not going to expect their workers to have a terminal emulator open 24/7.
I was just bashing Ubuntu's lack of purity with what seemed to be the most appropriate choice nowadays :-).
Most people don't care in the least. They just want a good acceptable solution where they can get help if they ever have a problem. Why would most people choose the mess of open source? Gimp vs Photoshop? Time is money.
The Open Source community is its own worst enemy.
Fedora is a rapidly changing distribution. RHEL/Clones have updates until 2020