Not trying to lure into an argument you're trying to avoid but I'm just curious; what is the religious argument about regarding port knocking? I know about both sides to tabs/spaces and vim/emacs but am curious what people have against port knocking.
In short, port knocking is a very, very short/weak password. And is a very weak authentication measure.
This is absolutely true and nobody could argue that.
So if you only did port knocking, or if you depended on port knocking, you're making a bad decision.
I believe in defense in depth, and therefore I think that port knocking on top of everything else you already do has good value - especially considering how simple and lightweight knockd is and my experience of it running stably for years at a time.