If they find the appeal to authority useful, I'd grab them a copy of _Software Engineering at Google_ and leave them a bookmark in "Help Me Hide My Code".
This is interesting and I agree with it. I think the problem is that it's not necessarily irrational insecurity. In computer science especially people can be very pedantic and quick to call out an individual or shut down the work of someone who is learning but is not yet on the same level of skill. Now if nothing is being hidden and all code is made public there is a big window for such criticism.
The thing is that, often, a developer already knows how to make their code better, solve their problem or get rid of some unnecessary abstraction. But they just don't have the time to do that. They don't have time for perfection. So when their work then gets criticized pedantically even though they already are aware of all those things it must be a very frustrating.
I certainly know what it's like to have the urge to rewrite something and I may on paper already know exactly what needs to be changed. Having something you know is imperfect out there feels stressful.
He is so insecure to talk to customers and iterate with them that it gets on my nerves.
He always have an ideal of "finished work" that, very often, we end delivering something not finished and/or wrong because we didn't iterate enough.
Customers not always know what they want even though they say that they know what they want.