Most of the west had/have bomb shelters and other things for a nuclear attack.

"Fairies and elves" suggest it's impossible. It isn't impossible, just very difficult. I'm here in bed conversing with someone on the other side of the world with a hand held device. The would have been "Fairies and elves" 50 years ago.

Preparing for unicorns would be fine if that was the only problem out there. However what's actually out there is buffer overflows, phishing, SQLI, and a bazillion other attacks being exploited on a global scale. So every bit of effort invested in preparing for unicorns is effort that's not invested in dealing with the massive amounts of attacks that are happening right now. It has negative utility.

It's like worrying about reinforcing the barn wall in front of you against komodo dragons when the other three walls of the barn are missing.