Sarcasm

"This whole Transaction [General Braddock's loss] gave us Americans the first Suspicion that our exalted Ideas of the Prowess of British Regulars had not been well founded."-The Autobiography of Benjamin Franklin

You snarky little devil you! You wrote this years after the American Revolution as a sort of critique that we didn't leave British sooner, didn't you?

I'm okay with the sarcasm.  I really am.  It's interesting to see how Franklin plays with the ideas of a glorious foundation that the American Colonies were built upon.  Especially, considering how this was written in the 1780s (for the part I'm referring, 1788) and we had just recently agreed upon a constitution and whatnot.  Although this letters look like they were intended to be private, I doubt that this is the case.
However, they do come off as less disagreeable, and it is interesting to see how sarcasm (an underrated virtue) can really help to establish your point better than coming out and directly saying it.