It depends on who’s vain, and why he is, And, why he’s boasting.
I didn’t read the good Christian’s screed, but can guess what was said and why he said it.
President Trump can and should be excused for being vain.
He can also be forgiven for boasting. Lesser men than him boast and many in the clegy praise these lesser men extravigantly.
So, Mr. President, be as vain and boastful as it takes to keep your good work going.
Some people lose sight of the fact that false modesty is, by definition, also a form of dishonesty.