Security through obscurity is a very valid way to secure something. It shouldn’t be the only way of securing something, but it can be a valid additional layer.

The knock sequence is a secret, just like a password. It may not be a particularly strong secret, but is is strong enough to keep out casual attackers. You’ll still need additional security, but sshd is well equipped to provide that.

Is it socially acceptable today? Maybe I’m biased by my location (western Europe), but Ive never seen people with fashist views getting widespread acceptance. Unfortunately that doesn’t the lone wolf from making quite a bit of noise, though.