Dear Paladini,
I believe I have fallen foul of the Comedic Grammar Police and if pushed I will make a fittingly full and complete confession. I'm sure you meant unimpeachable, not un-impeachable and I just wish I had used it too.
I plead an affliction of malapropism and throw myself upon the mercy of the PPRuNe Court.
Sincerely
Atlast