McArdle's view is very common - and is one reason Western Civilization is collapsing. It doesn't occur to people that if you're afraid of putting something in writing, then you shouldn't do that something you're afraid of putting in writing.
When people refuse to put things in writing, they are suspect. Why are they afraid of someone reading this?
Ethics is simple stuff. If you don't want other people to know about something, then don't do it.
I put everything in writing. I save every e-mail. Why? Because I'm not a scum bag. If I make a mistake, it will be an honest mistake. There have been times where my recollection of something has been wrong. I own my mistakes.
When I e-mail someone the terms of a deal and they answer by saying, "Call me to talk about this," then there is nothing to discuss. That person intends on cheating me.
Some people prefer to talk over the phone rather than has out details over e-mail. This is especially true of people over 50. In those cases, no big deal. Still, the phone conversation is going to be followed-up with an e-mail.
If someone under 50 wants to discuss stuff over the phone, let's record the conversation. Oh, you don't want to do that? Why not?
I love it when people refuse to put things in writing. It's the greatest "ethical tell" a person can give.
Life often demands we do business with the unethical. Most of us don't get cheated by the unethical - once we know not to trust the other side. Anyone who speaks rather than writes, nods rather than speaks, and wins rather than nods is intending on cheating you. Proceed accordingly.