In searching for "ignoscentes" I found an elegant putdown in my dictionary:
ignoratio elenchi
5L, ignorance of the refutation6 Logic a fallacious argument in which the conclusion reached or proposition proved is irrelevant to the matter at hand

Ignoratio would be a great name for a character in a book...

Sorry, can't resist.

Ignoratio 'ornblower and 'e'll sink you.

Only if you are a French man of war.